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15 Jan 2003

Volume 93, Issue 2, pp. 793-1329

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Nanoscale analysis on interfacial reactions in Al–Si–Cu alloys and Ti underlayer films

Jun-Mo Yang, Sukjae Lee, Ju-Chul Park, Deok-Won Lee, Tae-Kwon Lee, Jin-Tae Choi, Soun-Young Lee, Masahiro Kawasaki, and Tetsuo Oikawa

J. Appl. Phys. 93, 855 (2003); http://dx.doi.org/10.1063/1.1529070 (4 pages) | Cited 2 times

Online Publication Date: 27 December 2002

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Solid-phase reactions at the interface between sputtered Al–Si–Cu alloys and Ti films were investigated at the atomic scale by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy (EDS) coupled with a field-emission (scanning) transmission electron microscope. The analysis results showed that the interface is composed of an amorphous-like Ti–Si layer, an intermediate-crystalline layer, and a Si-dissolved TiAl3 layer containing dissolved Si TiAl3 with a crystallographic relationship with the Al film. The nanometer-scaled interlayers effectively play a role as a barrier suppressing the interdiffusion reaction of Al and Ti during annealing treatment. Further, the quantitative composition of the interlayers was revealed by the analysis of the intensity profiles obtained from EDS elemental maps. © 2003 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.Cc Kinetics of defect formation and annealing

Pulsed laser deposition of diamondlike carbon films on polycarbonate

Marco Bonelli, Antonio Miotello, Paolo Mosaner, Cinzia Casiraghi, and Paolo M. Ossi

J. Appl. Phys. 93, 859 (2003); http://dx.doi.org/10.1063/1.1530725 (7 pages) | Cited 11 times

Online Publication Date: 27 December 2002

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Diamondlike carbon films have been deposited on polycarbonate by pulsed laser deposition technique by irradiating highly oriented pyrolytic graphite with high-energy excimer laser pulses (248 nm wavelength, 20 ns duration, and up to 37 J/cm2 energy density). Irradiations were performed in different atmospheres: (1) moderate vacuum (10−2 Pa), (2) nitrogen atmosphere (1 Pa), and (3) argon atmosphere (1 Pa). The structure of the deposited films was analyzed with Raman spectroscopy. In vacuum-deposited films, a transition from mainly disordered graphitic carbon to up to 80% ta−C occurs above a laser energy density threshold of 7 J/cm2. No such transition was observed in films deposited in nitrogen up to energy densities as high as 33 J/cm2. In argon atmosphere the transition is only observed at high-laser energy density, ≈23 J/cm2. The results are discussed in terms of combined ballistic and chemical effects affecting both plume dynamics and bonding configuration of the growing film. The Fourier transform infrared spectroscopy showed that films deposited in nitrogen atmosphere contain nitrogen and hydrogen, thus becoming unstable when exposed to air. The hardness of ta−C coated polycarbonate, as measured by nanoindentation technique, is about 8 GPa, while when disordered graphitic carbon was deposited on the substrates hardness does not exceed 5 GPa. Measurement of the internal stress in the deposited films suggests that atomic relaxation occurs for laser-pulse energies exceeding 10 J/cm2, with residual stress values of the order of 1 GPa in films deposited in vacuum. In these conditions, given the strong interfacial chemical bonds, the adhesion strength is very high. In films deposited in nitrogen atmosphere the internal stress is almost constant for pulse laser energy up to 20 J/cm2 while it slowly increases at higher energies. © 2003 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
68.35.Gy Mechanical properties; surface strains
81.05.U- Carbon/carbon-based materials
62.20.Qp Friction, tribology, and hardness
68.35.Np Adhesion
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
68.60.Bs Mechanical and acoustical properties
81.40.Pq Friction, lubrication, and wear
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation

Ni/Si solid phase reaction studied by temperature-dependent current-voltage technique

Yu-Long Jiang, Guo-Ping Ru, Fang Lu, Xin-Ping Qu, Bing-Zong Li, and Simon Yang

J. Appl. Phys. 93, 866 (2003); http://dx.doi.org/10.1063/1.1527714 (5 pages) | Cited 14 times

Online Publication Date: 27 December 2002

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The temperature-dependent current–voltage (I–V–T) technique has been used to study the Ni/Si solid phase reaction by measuring the Schottky barrier height (SBH) inhomogeneity of Ni-silicide/Si Schottky diodes. The experimental results show the strong dependence of SBH inhomogeneity on the Ni/Si solid phase reaction. The SBH distribution of the diodes annealed at 500 and 600 °C can be described by a single-Gaussian function and the diode annealed at 500 °C is found to have the best homogeneity and the smallest leakage current. The SBH distribution of the diodes annealed at 400, 700, and 800 °C can be described by a double-Gaussian function in which the mean value of the second Gaussian function is substantially smaller than that of the dominant Gaussian function. The variation of SBH inhomogeneity, an interface property, is related to the phase evolution process in the Ni/Si solid phase reaction, and verified by reverse I–V measurements. Our results indicate that the I–V–T technique may be developed as a wafer-level testing tool to monitor the silicidation process in the complementary metal–oxide–semiconductor device fabrication. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing

Vacancy and interstitial depth profiles in ion-implanted silicon

P. Lévêque, H. Kortegaard Nielsen, P. Pellegrino, A. Hallén, B. G. Svensson, A. Yu. Kuznetsov, J. Wong-Leung, C. Jagadish, and V. Privitera

J. Appl. Phys. 93, 871 (2003); http://dx.doi.org/10.1063/1.1528304 (7 pages) | Cited 8 times

Online Publication Date: 27 December 2002

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An experimental method of studying shifts between concentration-versus-depth profiles of vacancy- and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy measurements utilizing the filling pulse variation technique. The vacancy profile, represented by the vacancy–oxygen center, and the interstitial profile, represented by the interstitial carbon–substitutional carbon pair, are obtained at the same sample temperature by varying the duration of the filling pulse. The effect of the capture in the Debye tail has been extensively studied and taken into account. Thus, the two profiles can be recorded with a high relative depth resolution. Using low doses, point defects have been introduced in lightly doped float zone n-type silicon by implantation with 6.8 MeV boron ions and 680 keV and 1.3 MeV protons at room temperature. The effect of the angle of ion incidence has also been investigated. For all implantation conditions the peak of the interstitial profile is displaced towards larger depths compared to that of the vacancy profile. The amplitude of this displacement increases as the width of the initial point defect distribution increases. This behavior is explained by a simple model where the preferential forward momentum of recoiling silicon atoms and the highly efficient direct recombination of primary point defects are taken into account. © 2003 American Institute of Physics.
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61.72.J- Point defects and defect clusters
71.55.Cn Elemental semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.S- Impurities in crystals

Surface modification of graphitic foam

Sharmila M. Mukhopadhyay, Rajasekhar V. Pulikollu, Erik Ripberger, and Ajit K. Roy

J. Appl. Phys. 93, 878 (2003); http://dx.doi.org/10.1063/1.1526155 (5 pages) | Cited 2 times

Online Publication Date: 27 December 2002

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This article discusses surface-related issues and possible modification approaches in high-porosity graphitic foam. The microcellular solid is made of graphitic carbon walls, ligaments, and beams supporting a network of interconnected pores. This makes the exposed surface area very high and its understanding a necessity for most applications. Graphitic planes are seen to be stacked at various orientations with respect to exposed surfaces. Therefore, a simplified analytical model that assumes “random” graphitic planes forming a three-dimensional array of tetrahedral cells may be an appropriate approximation. The influence of oxidizing chemicals such as nitric acid and hydrogen peroxide on surface properties has been studied using electron microscopy, photoelectron spectroscopy, and water absorption tests. Bulk properties such as density measurements and mechanical tests have been performed in parallel. It is seen that exposure to nitric acid results in an increase in oxygen-containing functional groups on the surface, which may lead to increased infiltration of polar matrix fluids such as water and epoxy resins. This possibility is further supported by water absorption studies that show increased water infiltration in foam after nitric acid treatment. Electron microscopy and density studies indicate that some surface etching occurs with concentrated nitric acid exposure, but not significant enough to decrease density. Strength of the stand-alone foam is reduced for concentrated nitric acid treatment, but the elastic modulus is unaffected. The scientific significance of these results in terms of future surface modification of microcellular solids has been discussed. © 2003 American Institute of Physics.
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81.05.Rm Porous materials; granular materials
81.65.Mq Oxidation
81.05.U- Carbon/carbon-based materials
61.43.Gt Powders, porous materials
82.70.Rr Aerosols and foams
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.60.Dp Adsorbed layers and thin films
68.35.Dv Composition, segregation; defects and impurities
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
62.20.-x Mechanical properties of solids
62.20.D- Elasticity

Electromigration model for the prediction of lifetime based on the failure unit statistics in aluminum metallization

Jong Ho Park and Byung Tae Ahn

J. Appl. Phys. 93, 883 (2003); http://dx.doi.org/10.1063/1.1528311 (10 pages) | Cited 5 times

Online Publication Date: 27 December 2002

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A failure model for electromigration based on the “failure unit model” was presented for the prediction of lifetime in metal lines.The failure unit model, which consists of failure units in parallel and series, can predict both the median time to failure (MTTF) and the deviation in the time to failure (DTTF) in Al metal lines. The model can describe them only qualitatively. In our model, both the probability function of the failure unit in single grain segments and polygrain segments are considered instead of in polygrain segments alone. Based on our model, we calculated MTTF, DTTF, and activation energy for different median grain sizes, grain size distributions, linewidths, line lengths, current densities, and temperatures. Comparisons between our results and published experimental data showed good agreements and our model could explain the previously unexplained phenomena. Our advanced failure unit model might be further applied to other electromigration characteristics of metal lines. © 2003 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
85.30.De Semiconductor-device characterization, design, and modeling

Evolution of normal stress and surface roughness in buckled thin films

G. Palasantzas and J. Th. M. De Hosson

J. Appl. Phys. 93, 893 (2003); http://dx.doi.org/10.1063/1.1528299 (5 pages) | Cited 6 times

Online Publication Date: 27 December 2002

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In this work we investigate buckling of compressed elastic thin films, which are bonded onto a viscous layer of finite thickness. It is found that the normal stress exerted by the viscous layer on the elastic film evolves with time showing a minimum at early buckling stages, while it increases at later stages. The normal stress also shows a minimum as a function of applied compressive stress, which depends strongly on the viscosity of the underlying layer and strain values. Furthermore, with decreasing viscosity the film roughness amplitude also shows a minimum at early buckling stages. The effect of the viscosity becomes more pronounced with increasing strain in the film. Finally, decreasing elastic film thickness and/or increasing viscous layer thickness also enhance buckling roughness. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
46.32.+x Static buckling and instability
68.55.-a Thin film structure and morphology
62.20.F- Deformation and plasticity
68.35.B- Structure of clean surfaces (and surface reconstruction)
46.35.+z Viscoelasticity, plasticity, viscoplasticity
46.25.Cc Theoretical studies

Self-affine roughness effects on the contact area between elastic bodies

G. Palasantzas and J. Th. M. De Hosson

J. Appl. Phys. 93, 898 (2003); http://dx.doi.org/10.1063/1.1528300 (5 pages) | Cited 2 times

Online Publication Date: 27 December 2002

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We have calculated the real contact area between elastic bodies with self-affine rough surfaces, which are described in terms of analytical correlation models in Fourier space. It is found that the roughness has a strong influence on the real contact area A(λ) at lateral length scales λ which are comparable with the in-plane roughness correlation length ξ, and for significant applied loads σo beyond the linear regime (or A∝σo). The effect of the roughness exponent H can be rather complex, depending on the relative magnitude of the roughness correlation length ξ with respect to the lateral length scale λ where the contact area is considered. Finally, we also show that descriptions of the influence of the roughness that is only based on power law approximations of the self-affine roughness spectrum are rather insufficient, especially for large roughness exponents H (>0.5). © 2003 American Institute of Physics.
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46.55.+d Tribology and mechanical contacts
46.25.Cc Theoretical studies
68.35.B- Structure of clean surfaces (and surface reconstruction)
62.20.D- Elasticity

Formation of Au0.6Ge0.4 alloy induced by Au-ion irradiation of Au/Ge bilayer

T. Som, P. Ayyub, D. Kabiraj, N. Kulkarni, V. N. Kulkarni, and D. K. Avasthi

J. Appl. Phys. 93, 903 (2003); http://dx.doi.org/10.1063/1.1530356 (4 pages) | Cited 11 times

Online Publication Date: 27 December 2002

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We report on the formation of a-axis oriented Au0.6Ge0.4 alloy on a Si(100) substrate on 120 MeV Au-ion irradiation of a Au/Ge bilayer and subsequent vacuum annealing at 360 °C. Irradiation-induced changes occurring across the Au/Ge interface were studied using Rutherford backscattering spectrometry. Phase identification was done by x-ray diffraction and the surface morphology of the samples was studied by scanning electron microscopy. Formation of oriented Au0.6Ge0.4 alloy was confirmed by transmission electron microscopy and discussed on the basis of swift heavy ion induced effects followed by thermal annealing. © 2003 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
61.80.Jh Ion radiation effects
61.82.Bg Metals and alloys
85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
68.35.B- Structure of clean surfaces (and surface reconstruction)

Self-diffusion of boron in TiB2

H. Schmidt, G. Borchardt, C. Schmalzried, R. Telle, S. Weber, and H. Scherrer

J. Appl. Phys. 93, 907 (2003); http://dx.doi.org/10.1063/1.1530715 (5 pages) | Cited 7 times

Online Publication Date: 27 December 2002

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Self-diffusion studies of boron in polycrystalline TiB2 were carried out as a function of temperature, using a specially designed experiment with stable 10B tracers, 11B−enriched TiB2 samples, and secondary ion mass spectrometry for depth profiling. The diffusivities were extracted from the isotope depth profiles in the range between 950 and 1600 °C. They obey an Arrhenius behavior with an activation enthalpy of about ΔH=2.2 eV and a preexponential factor of D0=4×10−12 m2/s. Interpolation of the diffusivities to the melting point of 3225 °C reveals a very low value of about D(Tm)≈10−15 m2/s, which reflects the covalent bonds present in the material. A possible explanation for the low values obtained for D0 and ΔH is the assumption of a diffusion mechanism via vacancies, where in addition to thermal vacancies a substantial concentration of structural vacancies are present. The possible influence of grain boundaries and of the anisotropic crystal structure on the results is discussed together with crystallographic diffusion paths. © 2003 American Institute of Physics.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
61.72.J- Point defects and defect clusters
65.40.G- Other thermodynamical quantities
61.72.Mm Grain and twin boundaries
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
61.66.Bi Elemental solids
61.66.Dk Alloys

Thermal stability and electron irradiation effect on Zr-based amorphous alloys

T. Nagase and Y. Umakoshi

J. Appl. Phys. 93, 912 (2003); http://dx.doi.org/10.1063/1.1529073 (7 pages) | Cited 27 times

Online Publication Date: 27 December 2002

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Specimens of Zr66.7Cu33.3, Zr65.0Al7.5Cu27.5, and Zr65.0Al7.5Ni10.0Cu17.5 amorphous alloys with different thermal stability were irradiated by high energy electrons at an accelerated voltage of 2000 and 1000 kV. Electron irradiation was performed at 298 and 103 K. Crystallization of three amorphous alloys was accelerated by this irradiation and nanocrystalline structures were obtained. The critical total dose required for crystallization of the amorphous phase by electron irradiation depends strongly on the irradiation temperature and stability of this amorphous phase. The phase stability and crystallization behavior of the amorphous phase are discussed based on the electron irradiation effect. © 2003 American Institute of Physics.
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61.82.Bg Metals and alloys
61.80.Fe Electron and positron radiation effects
61.43.Fs Glasses
61.46.-w Structure of nanoscale materials
81.05.Kf Glasses (including metallic glasses)
64.70.K- Solid-solid transitions
61.82.Rx Nanocrystalline materials

Contact angle measurements for adhesion energy evaluation of silver and copper films on parylene-n and SiO2 substrates

Kaustubh S. Gadre and T. L. Alford

J. Appl. Phys. 93, 919 (2003); http://dx.doi.org/10.1063/1.1530362 (5 pages) | Cited 9 times

Online Publication Date: 27 December 2002

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Copper and silver films are being considered for future multilevel interconnect systems. The reduction of feature size has also demanded the use of different low-dielectric materials (e.g., parylenes) in place of conventional silicon dioxide based layers. Adhesion of these materials with each other is a major hurdle in the reliable and durable performance of the devices. Contact angle measurements are used to measure adhesion energies of Cu and Ag layers on substrates of either SiO2 and Pa–n. Qualitative tape-test analysis indicates improved adhesion of these films with anneal and plasma treatment. Surface energy increase of parylene–n using oxygen plasma treatment is demonstrated using sessile water-drop method. The increase in adhesion for the Ag/Pa–n system is attributed to increased roughness and presence of carbonyl groups on the surface. The contact angle measurements are corrected to compensate for the effect of roughness. The adhesion energy for Ag/Pa–n system increases from 0.33 to 1.28 N/m with plasma treatment. Higher-surface energies of copper at room temperature attribute to higher-copper adhesion energy when compared to that of silver. © 2003 American Institute of Physics.
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68.35.Np Adhesion
68.35.Md Surface thermodynamics, surface energies
85.40.Ls Metallization, contacts, interconnects; device isolation
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
52.77.-j Plasma applications

Ultrathin Ag films on H:Si(111)-1×1 surfaces deposited at low temperatures

T. Müller and H. Nienhaus

J. Appl. Phys. 93, 924 (2003); http://dx.doi.org/10.1063/1.1530714 (6 pages) | Cited 15 times

Online Publication Date: 27 December 2002

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The growth, structure, and electronic properties of thin Ag films on H-terminated Si(111) surfaces were investigated with Auger electron and photoelectron spectroscopy (and atomic force and secondary electron microscopy). The films were either evaporated at room temperature (RT) or deposited at low temperature (LT) and subsequently annealed to RT in the thickness range between 1 and 50 monolayers (0.2–12 nm). The LT preparation leads to large Ag islands on a wetting monolayer which form a continuous Ag film above a critical thickness of 30 monolayers. Ultraviolet photoelectron spectra and work function measurements reveal a (111) surface orientation of the Ag islands. In constrast, RT deposition results in Stranski-Krastanov growth of smaller and irregularly shaped islands which do not form a continuous layer even up to film thicknesses of 45 monolayers. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
73.20.At Surface states, band structure, electron density of states
79.60.Dp Adsorbed layers and thin films
73.30.+y Surface double layers, Schottky barriers, and work functions
79.20.Fv Electron impact: Auger emission
68.37.Ps Atomic force microscopy (AFM)
79.20.Hx Electron impact: secondary emission
81.05.Bx Metals, semimetals, and alloys

Effects of annealing ambient on the formation of compensation defects in InP

A. H. Deng, P. Mascher, Y. W. Zhao, and L. Y. Lin

J. Appl. Phys. 93, 930 (2003); http://dx.doi.org/10.1063/1.1531230 (3 pages) | Cited 3 times

Online Publication Date: 27 December 2002

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Positron annihilation lifetime (PAL) and photoinduced current transient spectroscopies (PICTS) have been employed to study the formation of compensation defects in undoped InP under different annealing processes with pure phosphorus (PP) ambience and iron phosphide (IP) ambience, respectively. The different annealing ambiences convert the as-grown n-type undoped InP into two types of semi-insulating (SI) states. The positron average lifetimes of as-grown InP, PP SI-InP, and IP SI-InP are found to be 246, 251, and 243 ps, respectively, which are all longer than the bulk lifetime of 240 ps, indicating the existence of vacancy-type positron-trapping defects. For as-grown InP, VInH4 complexes are the dominant defects. They dissociate into VInHn(0⩽n⩽3) acceptor vacancies under PP ambience annealing, compensating the residual shallow donors and turning the material semi-insulating. In forming IP SI-InP, diffusion of iron into VIn complexes under IP ambience annealing produces the substitutional compensation defect FeIn, causing a shorter positron average lifetime. The PICTS measurements show that a group of vacancy-type defects has been suppressed by iron diffusion during the annealing process, which is in good agreement with the PAL results. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
78.70.Bj Positron annihilation
72.40.+w Photoconduction and photovoltaic effects
66.30.J- Diffusion of impurities
72.80.Ey III-V and II-VI semiconductors

Infrared and Raman spectroscopy of [Pb(Zn1/3Nb2/3)O3]0.92–[PbTiO3]0.08 and [Pb(Mg1/3Nb2/3)O3]0.71–[PbTiO3]0.29 single crystals

S. Kamba, E. Buixaderas, J. Petzelt, J. Fousek, J. Nosek, and P. Bridenbaugh

J. Appl. Phys. 93, 933 (2003); http://dx.doi.org/10.1063/1.1528274 (7 pages) | Cited 42 times

Online Publication Date: 27 December 2002

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Far-infrared reflectivity spectra of [Pb(Zn1/3Nb2/3)O3]0.92–[PbTiO3]0.08 and [Pb(Mg1/3Nb2/3)O3]0.71–[PbTiO3]0.29 single crystals were investigated between 10 and 530 K, micro-Raman spectra were recorded between 300 and 800 K. No phonon softening was observed near either of the ferroelectric phase transitions. The low-frequency dielectric anomaly in the paraelectric phase is caused by contribution of dynamic polar nanoclusters with the main dispersion in the microwave range. Infrared and Raman spectra confirm the locally doubled unit cell (Zprim=2) in the paraelectric and ferroelectric phases due to the ordering in the perovskite B sites and occurrence of polar nanoclusters in the paraelectric phase. The lowest-frequency transverse optical (TO1) phonon mode active in the infrared spectra is underdamped in contrast to the recent result of inelastic neutron scattering, where no TO1 mode could be observed for the wave vectors q⩽0.2 Å−1. This discrepancy was explained by different q vectors probed in infrared and neutron experiments. The infrared probe couples with very long-wavelength phonons (q≈10−5 Å−1) which see the homogeneous medium averaged over the nanoclusters, whereas the neutron probe couples with phonons whose wavelength is comparable to the nanocluster size (q⩾10−2 Å−1). © 2003 American Institute of Physics.
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78.30.Hv Other nonmetallic inorganics
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
77.80.B- Phase transitions and Curie point
61.46.-w Structure of nanoscale materials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
61.66.Fn Inorganic compounds

Elastic modulus of amorphous boron suboxide thin films studied by theoretical and experimental methods

Denis Music, Ulrich Kreissig, Valeriu Chirita, Jochen M. Schneider, and Ulf Helmersson

J. Appl. Phys. 93, 940 (2003); http://dx.doi.org/10.1063/1.1531811 (5 pages) | Cited 9 times

Online Publication Date: 27 December 2002

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Boron suboxide BOx thin films have been deposited on Si (100) by reactive rf magnetron sputtering of B powders in an Ar/O2 atmosphere. Elastic recoil detection analysis and x-ray diffraction were used to study the influence of the O incorporation on the film composition and structure and relate them to mechanical properties, which were evaluated by nanoindentation. As x in BOx was increased from 0.08 to 0.18, the elastic modulus of the x-ray amorphous films decreased from 273 to 231 GPa, by 15%. This can be understood using classical molecular dynamics (MD) with a Buckingham-like interaction potential: The increase in the O concentration and corresponding formation of B–O bonds, shown to be longer than the B–B bonds, resulted in larger ionic contributions as well as a density reduction. This increased ionicity was responsible for the observed decrease in elastic modulus. As even more O was incorporated (x>0.18), the H concentration increased, exceeding 0.3 at. %. This may cause the formation of boric acid (H3BO3) as a result of the chemical reaction with H2O upon atmosphere exposure. The presence of van der Waals and hydrogen bonding, associated with H3BO3 formation, provides a reasonable explanation for the extensive decrease in elastic modulus from 231 to 15 GPa, by 94%. The parameterization for the Buckingham-like interaction potential, introduced in this study, can be used for MD simulations of amorphous BOx systems without H3BO3. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.15.Cd Deposition by sputtering
61.43.Er Other amorphous solids
68.55.-a Thin film structure and morphology
61.43.Bn Structural modeling: serial-addition models, computer simulation
62.20.M- Structural failure of materials

Development of microstructure in Cr and Cr/CoCrPt films made by pulsed laser deposition

M. Shima and C. A. Ross

J. Appl. Phys. 93, 945 (2003); http://dx.doi.org/10.1063/1.1529295 (6 pages) | Cited 2 times

Online Publication Date: 27 December 2002

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Cr films and Cr/CoCrPt bilayer films have been grown using ion-beam-assisted pulsed laser deposition (PLD). High mobility conditions such as a substrate temperature above 350 °C, a low deposition rate, and a high laser energy promote the formation of a {100} bcc crystallographic preferred orientation in the Cr layer, while a {110}-oriented film is formed under other conditions. The {100} orientation can be formed at lower temperatures if the film is bombarded by energetic Ar ions during growth. CoCrPt grows with the hcp-{11math0} orientation on bcc-Cr {100} underlayers, which is the same epitaxial relationship that occurs in sputtered Cr/Co-alloy films used in hard disk recording media. PLD CoCrPt films also have magnetic properties broadly similar to those of sputtered films. The PLD film microstructure development is interpreted in terms of the preferential nucleation of {100}-oriented Cr crystals during the early stages of film growth. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Forbidden transitions and the effective masses of electrons and holes in In1−xGaxAs/InP quantum wells with compressive strain

Jun Shao, Achim Dörnen, Enno Baars, Volker Härle, Ferdinand Scholz, Shaoling Guo, and Junhao Chu

J. Appl. Phys. 93, 951 (2003); http://dx.doi.org/10.1063/1.1527709 (6 pages) | Cited 1 time

Online Publication Date: 27 December 2002

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Two types of forbidden transitions are identified in In1−xGaxAs/InP undoped quantum wells (QWs) with compressive strain by low-temperature (1.8 K) magneto-optical absorption. One of them is due to the interband transitions with different principal quantum numbers and is observable mainly in a low magnetic field and the other corresponds to P- and D-type exciton states and gets stronger as the magnetic field increases. By analyzing the forbidden transitions the in-plane effective masses of electrons (me,ρ∗) and heavy holes (mh,ρ∗) are simultaneously determined, together with the z-direction (growth-direction) ones (me,z∗,mh,z∗). The theoretically predicted relation among the electron effective masses [Sugawara et al., Phys. Rev. B 48, 8102 (1993)], me,Γ6<me,ρ∗<me,z∗, where me,Γ6 is the band-edge electron effective mass of bulk material, is therefore verified. The difference between the values of me,z∗ and me,ρ∗ is found to decrease as the strain in the QW drops. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
78.20.Ls Magneto-optical effects
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Heating-rate method for determination of kinetic parameters from thermally stimulated conductivity and luminescence

A. Opanowicz and P. Pietrucha

J. Appl. Phys. 93, 957 (2003); http://dx.doi.org/10.1063/1.1530713 (11 pages) | Cited 1 time

Online Publication Date: 27 December 2002

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A method for determining the ratio of the recombination and trapping coefficients and the relative density of inactive deep traps on the basis of simultaneously measured thermally stimulated conductivity (TSC) and luminescence (TSL) is derived in the case of a temperature-dependent free electron lifetime. The method is based on the relation between the preexponential factor of the temperature dependence of the thermally stimulated free electron density (TSC) and the occupancy of active traps. Values of the preexponential factor and the trap depth corresponding to different values of the relative TSC intensity can be found from the TSC peak measured at different heating rates of the sample. Similar analysis of the TSL peak produces accurate values of the trap depth as well. The method for determination of the trap depth also yields accurate results from multipeak TSC and TSL curves. These results are more accurate than those found using the heating-rate method of Haering and Adams [Phys. Rev. 117, 451 (1960)], the initial-rise method of Garlick and Gibson [Proc. Phys. Soc. (London) 60, 574 (1948)], and the fractional TSL method of Gobrecht and Hofmann [J. Phys. Chem. Solids 27, 509 (1960)]. © 2003 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.60.Kn Thermoluminescence
71.55.-i Impurity and defect levels
77.22.Ej Polarization and depolarization

Dynamic response of ceramic-metal composites: The TiC-Steel system

B. Klein, N. Frage, M. P. Dariel, and E. Zaretsky

J. Appl. Phys. 93, 968 (2003); http://dx.doi.org/10.1063/1.1530719 (9 pages) | Cited 3 times

Online Publication Date: 27 December 2002

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The dynamic response of a titanium carbide (TiC)–carbon steel, ceramic-metal composite, was studied in planar impact experiments, using a copper impactor with velocity in the 80–450 m/s range. The composites were prepared by pressureless infiltration of TiC ceramic preforms by molten steel. The metallic component had either a pearlitic or a martensitic microstructure, determined by an appropriate heat treatment. Fully dense composites, consisting of TiC and 1060 steel, in pearlitic and martensitic states, were used as reference samples. Values of the Hugoniot elastic limit and of the spall strength were derived from the velocity interferometer system for any refractor records of the free surface velocity profiles of the impacted samples. These properties are affected drastically by the confining stress that is induced in the TiC particles by the steel submatrix and is dependent on the microstructure of the latter. The results show unambiguously that the dynamic response of the cermets may be controlled by choosing an appropriate thermal treatment. © 2003 American Institute of Physics.
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81.05.Mh Cermets, ceramic and refractory composites
81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Gh Other heat and thermomechanical treatments
62.20.F- Deformation and plasticity
62.20.D- Elasticity
62.20.Qp Friction, tribology, and hardness
62.65.+k Acoustical properties of solids

Spectroscopic properties and thermal stability of erbium-doped bismuth-based glass for optical amplifier

Jianhu Yang, Shixun Dai, Yuefen Zhou, Lei Wen, Lili Hu, and Zhonghong Jiang

J. Appl. Phys. 93, 977 (2003); http://dx.doi.org/10.1063/1.1531840 (7 pages) | Cited 63 times

Online Publication Date: 27 December 2002

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The spectroscopic properties and thermal stability of Er2O3 doped Bi2O3–B2O3–Na2O glasses are investigated experimentally. A close correlation is observed between the B2O3 content and the spectroscopic properties such as Judd–Ofelt intensity parameters Ωt (t=2,4,6), emission spectra, and lifetime of 4I13/2 level of Er3+. The value of Ω6 increases with an increase of B2O3 content, which is attributed to the decrease of the covalency of Er–O bond in terms of the glass microstructure and electronegativity theory. The emission spectra of 4I13/2→4I15/2 transition broadens as a consequence of the enhancement of the inhomogeneous distribution of Er3+ sites when increasing B2O3 content. The lifetime of 4I13/2 level of Er3+ in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B–O bond, the large refractive index of the host, and the existence of OH− in the glass. In addition, the glass stability is improved in which the substitution of B2O3 for Bi2O3 strengthens the network structure. The suitability of bismuth-based glass as a host for Er3+ doped for a broadband amplifier and its advantages over other glass hosts are also discussed. © 2003 American Institute of Physics.
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42.70.Ce Glasses, quartz
78.55.Qr Amorphous materials; glasses and other disordered solids
61.43.Fs Glasses
78.40.Pg Disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Characterization of porous indium tin oxide thin films using effective medium theory

J. Ederth, G. A. Niklasson, A. Hultåker, P. Heszler, C. G. Granqvist, A. R. van Doorn, M. J. Jongerius, and D. Burgard

J. Appl. Phys. 93, 984 (2003); http://dx.doi.org/10.1063/1.1532934 (5 pages) | Cited 13 times

Online Publication Date: 27 December 2002

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Effective medium theory was used to model optical properties in the 0.3 – 30 μm wavelength range for films comprised of nanoparticles of a transparent conducting oxide that are connected in a percolating network characterized by a filling factor f. The model is based on charge carrier density ne and resistivity ρ of the particles, and it enables analyses of these microscopic parameters upon posttreatment of the film. The theory was used to interpret data on spin coated layers consisting of nanoparticles of indium tin oxide (i.e., In2O3:Sn) with f close to the percolation limit. It showed that the as-deposited film contained nanoparticles with ne as large as ∼5×1020 cm−3 and ρ≈5×10−4 Ω cm. The model also provided important data on f, ne, and ρ after heat treatment of the film. © 2003 American Institute of Physics.
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78.66.Li Other semiconductors
73.61.Le Other inorganic semiconductors
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.40.Fy Semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.20.Fr Low-field transport and mobility; piezoresistance

Interface properties and structural evolution of TiN/Si and TiN/GaN heterostructures

P. Patsalas and S. Logothetidis

J. Appl. Phys. 93, 989 (2003); http://dx.doi.org/10.1063/1.1531812 (10 pages) | Cited 40 times

Online Publication Date: 27 December 2002

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Spectroscopic ellipsometry (SE) is employed to study the evolution of microstructure, stoichiometry, and electron-transport properties of titanium nitride (TiN) heterostructures grown on Si and gallium nitride (GaN) by reactive magnetron sputtering. In order to achieve subnanometer resolution for the SE analysis, we developed and validated the appropriate methods of interpreting the optical data. Thus, we used (a) effective medium theories describing the heterostructures in terms of their constituent materials (Si, GaN, TiN, over-stoichiometric TiNx, and voids), and (b) a combined Drude–Lorentz model describing the optical response of the conduction and valence electrons of TiN and TiNx. In the case of TiN/Si, the SE results indicate a pure Volmer–Weber type of growth with four distinct growth stages. A TiNx layer is formed before TiN due to the stress variations during growth. On the other hand, TiN/GaN exhibits a quasi two-dimensional growth character. In both cases, the TiN resistivity is very high for films thinner than the critical thickness for homogeneous growth. Thus, for practical applications in electronic devices the thickness of the TiN layer should be at least 4 and 14 nm for TiN/GaN and TiN/Si, respectively. © 2003 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.66.Bi Elemental solids
61.66.Dk Alloys
68.47.Fg Semiconductor surfaces
73.40.-c Electronic transport in interface structures

Optical absorption in Co-doped SiO2-GeO2 glass rods and fibers

Yuichi Morishita and Keiji Tanaka

J. Appl. Phys. 93, 999 (2003); http://dx.doi.org/10.1063/1.1531815 (5 pages) | Cited 2 times

Online Publication Date: 27 December 2002

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Optical absorption spectra in rods and fibers of Co-doped SiO2-GeO2 glass have been studied comparatively, and the result is extended to other transition-metal ions. In the glass with a high-Co concentration (≈2000 wt. ppm), absorption peaks due to Co2+ ions appear differently in the rod and the fiber. A deconvolution analysis shows that this difference arises from the ratio of CoO4 and CoO6 units, the latter being preferred in the rod. This observation can be understood in terms of fictive temperature and free energy. The thermodynamical idea is also applied to the coordination behavior of other transition-metal ions in oxides, which suggests a close correlation between glasses and crystals. Results for a low-Co-concentration glass are also discussed. © 2003 American Institute of Physics.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.40.Pg Disordered solids
71.70.Ch Crystal and ligand fields

Influence of dynamic annealing on the shape of channeling implantation profiles in Si and SiC

M. Posselt, L. Bischoff, J. Teichert, and A. Ster

J. Appl. Phys. 93, 1004 (2003); http://dx.doi.org/10.1063/1.1533092 (10 pages) | Cited 8 times

Online Publication Date: 27 December 2002

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The influence of the dose rate and temperature on the dose dependence of the shape of Ge depth profiles obtained by channeling implantation into Si and SiC is investigated. A focused ion-beam system is employed which enables the application of two widely different dose rates (1011 and 1018 cm−2 s−1). Implantations into Si are performed at room temperature (RT) and 250 °C. SiC is implanted at RT, 225, 450, and 580 °C. The Ge depth distributions are measured by secondary ion mass spectrometry. The shape of the channeling implantation profiles is affected by the formation and evolution of complex defects formed during ion bombardment, since these defects cause significant dechanneling of the implanted particles. The competing influence of the dose rate and temperature on the shape of Ge depth profiles is explained in terms of intracascade defect relaxation. The time scale for the reduction of complex defects is estimated. At RT, in Si some defect relaxation occurs within the first 100 s after an ion impact. At temperatures of 225 and 250 °C, in SiC and Si, a considerable defect reduction is found within the first 10 μs as well as between 10 μs and 100 s after an ion impact. The complex defects in Si vanish entirely between 10 μs and 100 s, whereas in SiC some of them survive. At 450 and 580 °C, defects in SiC relax mainly within the first 10 μs after an ion impact. The defect reduction increases with growing implantation temperature. Different mechanisms which may be responsible for the dynamic annealing in Si and SiC are discussed. A phenomenological model is developed in order to treat the dose rate and temperature dependence of the defect-induced dechanneling within the framework of atomistic computer simulations of ion implantation. The simulated Ge depth profiles agree very well with the measured data. © 2003 American Institute of Physics.
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61.72.S- Impurities in crystals
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.uf Ge and Si
61.72.up Other materials
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