jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

14 Jan 2013

Volume 113, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 113, 021301 (2013); http://dx.doi.org/10.1063/1.4757907 (101 pages)

Ville Miikkulainen, Markku Leskelä, Mikko Ritala, and Riikka L. Puurunen
Enlarge Image | Read More
Page 1 of 5 Pages Next Page | Jump to Page
back to top
RSS Feeds

Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

Ville Miikkulainen, Markku Leskelä, Mikko Ritala, and Riikka L. Puurunen

J. Appl. Phys. 113, 021301 (2013); http://dx.doi.org/10.1063/1.4757907 (101 pages) | Cited 5 times

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.
Show PACS
68.55.ag Semiconductors
81.05.Dz II-VI semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
back to top
RSS Feeds
back to top Lasers, Optics, and Optoelectronics

The luminescence characteristics of CsI(Na) crystal under α and X/γ excitation

Jinliang Liu, Fang Liu, Xiaoping Ouyang, Bin Liu, Liang Chen, Jinlu Ruan, Zhongbing Zhang, and Jun Liu

J. Appl. Phys. 113, 023101 (2013); http://dx.doi.org/10.1063/1.4773528 (4 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, we study the effective decay time characteristic of CsI(Na) crystal under 239Pu alpha particle and 137Cs gamma-ray excitation using a single photon counting decay time measurement system. The measurement system employs a silicon optical fiber to couple and transit single photon. The slow decay time component of CsI(Na) crystal is 460–550 ns. We observe a 15 ns fast decay component under alpha particle excitation. In addition, we find that the primary stage of the falling edge in the decay time curve is non-exponential and drops rapidly when CsI(Na) crystal is excited by 239Pu alpha particles. Since the high density of self-trapped-excitons (STEs) is produced in alpha particle excitation process, we propose that the fast falling edge is corresponding to the quenching process of STEs which transit with non-radiation in the case of high excitation density. To prove this proposal, we excited the CsI(Na) crystal with sub-nanosecond intensive pulsed X-ray radiation. Our X-ray impinging results show that the fast falling edge also exists under low energy (average 100 keV) bremsstrahlung X-ray excitation.
Show PACS
78.55.Hx Other solid inorganic materials
61.80.Cb X-ray effects
61.80.Ed γ-ray effects
61.80.Jh Ion radiation effects
71.35.Aa Frenkel excitons and self-trapped excitons

Study of the formation of 3-D titania nanofibrous structure by MHz femtosecond laser in ambient air

Amirhossein Tavangar, Bo Tan, and K. Venkatakrishnan

J. Appl. Phys. 113, 023102 (2013); http://dx.doi.org/10.1063/1.4771667 (9 pages)

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this study, we describe the formation mechanism of web-like three-dimensional (3-D) titania nanofibrous structures during femtosecond laser ablation of titanium (Ti) targets in the presence of background air. First, we demonstrate the mechanism of ablation of Ti targets by multiple femtosecond laser pulses at ambient air in an explicit analytical form. The formulas for evaporation rates and the number of ablated particles, which is analogous to the deposition rate of the synthesized nanofibers, for the ablation by a single pulse and multiple pulses as a function of laser parameters, background gas, and material properties are predicted and compared to experimental results. Afterwards, the formation of nanofibrous structures is demonstrated by applying an existing simplified kinetic model to Ti targets and ambient conditions. The predicted theory provides nanofiber diameter dependency with the combination of laser parameters, target properties, and ambient gas characteristics. Experimental studies are then performed on titania nanofibrous structures synthesized by laser ablation of Ti targets using MHz repletion-rate femtosecond laser at ambient air. The models' predictions are then compared with the experimental results, where nanostructures with different morphologies are manufactured by altering laser parameters. Our results indicate that femtosecond laser ablation of Ti targets at air background yields crystalline titania nanostructures. The formation of crystalline titania nanostructures is preceded by thermal mechanism of nucleation and growth. The results point out that laser pulse repetition and dwell time can control the density, size, and pore size of the engineered nanofibrous structure. As the deposition rate of nanostructures is analogous to the ablation rate of the target, higher density of nanofibrous structure is seen at greater laser fluences. The predicted theory can be applied to predict ablation mechanism and nanofiber formation of different materials.
Show PACS
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.05.Rm Porous materials; granular materials
81.15.Fg Pulsed laser ablation deposition
81.16.-c Methods of micro- and nanofabrication and processing
52.38.Mf Laser ablation
61.43.Gt Powders, porous materials

Electrical and optical properties of p-type CuFe1-xSnxO2 (x = 0.03, 0.05) delafossite-oxide

Chesta Ruttanapun, Banjong Boonchom, Montree Thongkam, Samart Kongtaweelert, Chanchana Thanachayanont, and Aree Wichainchai

J. Appl. Phys. 113, 023103 (2013); http://dx.doi.org/10.1063/1.4773335 (6 pages)

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The CuFe1-xSnxO2 (x = 0.03, 0.05) delafossite samples have been synthesized by a solid-state reaction to investigate electrical and optical properties of the transparent conducting oxide materials. Crystal structure was characterized by XRD. The electrical conductivity and Seebeck coefficient were measured in the high temperature range of 300 to 960 K, while the Hall coefficient, XPS, and UV-VIS-NIR spectra were analyzed at room temperature. The XRD peaks of the samples indicate the delafossite structure phase, and the XPS spectra reveal the stable Sn2+-doping state. The Seebeck and Hall coefficient display a positive sign indicating the p-type conducting oxide. The optical allowed direct gap is 3.45 eV as a visible-transparent material. The activation energies for polaron hopping between Sn2+ sites and Fe3+ sites of 36 and 32 meV are obtained from the samples having x = 0.03 and 0.05, respectively. The CuFe1-xSnxO2 delafossite oxide compounds, of which the Fe3+ sites in the CuFeO2 are substituted by the Sn2+ ions, are p-type transparent conducting oxide materials. The activation energy is found to decrease with an increased in Sn content.
Show PACS
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.10.Dn Growth from solutions
61.66.Fn Inorganic compounds
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Pa Thermoelectric and thermomagnetic effects
72.80.Sk Insulators

Charge transport properties in electrically aged organic light-emitting diodes

R. Huber, F. Witt, H. Borchert, E. von Hauff, S. Heun, H. Buchholz, and J. Parisi

J. Appl. Phys. 113, 023104 (2013); http://dx.doi.org/10.1063/1.4774409 (5 pages)

Online Publication Date: 14 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Organic light-emitting diodes (OLEDs) are a rapidly developing technology with high innovation potential for displays, lighting, and further applications. Critical issues for current research remain the extension of lifetimes and, related to this aim, a deeper understanding of degradation processes in OLEDs. In the present work, we used the charge-based deep level transient spectroscopy technique to investigate changes in the charge transport in OLEDs induced by electrical aging. Both trap states capturing electrons and holes, respectively, were detected. Temperature-dependent measurements enabled estimating the depth of the trap states for electrons. Comparison of spectra of electrically aged and undriven devices revealed that aging seemed to increase the density of traps but did not lead to the occurrence of new types of trap states. Furthermore, experiments with different voltage pulses to fill the charge carrier trap states allowed conclusions on age-induced changes of the injection barrier for holes.
Show PACS
85.60.Jb Light-emitting devices
back to top Plasmas and Electrical Discharges

A first principles study of the lattice stability of diamond-structure semiconductors under intense laser irradiation

ShiQuan Feng, JianLing Zhao, and XinLu Cheng

J. Appl. Phys. 113, 023301 (2013); http://dx.doi.org/10.1063/1.4772596 (6 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using density-functional linear-response theory, we calculated the phonon dispersion curves for the diamond structural elemental semiconductors of Ge, C and zinc-blende structure semiconductors of GaAs, InSb at different electronic temperatures. We found that the transverse-acoustic phonon frequencies of C and Ge become imaginary as the electron temperature is elevated, which means the lattices of C and Ge become unstable under intense laser irradiation. These results are very similar with previous theoretical and experimental results for Si. For GaAs and InSb, not only can be obtained the similar results for their transverse-acoustic modes, but also their LO-TO splitting gradually decreases as the electronic temperature is increased. It means that the electronic excitation weakens the strength of the ionicity of ionic crystal under intense laser irradiation.
Show PACS
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
71.15.-m Methods of electronic structure calculations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Field emission model of carbon nanotubes to simulate gas breakdown in ionization gas sensor

Salman Mahmood, Zainal Arif Burhanudin, and Aysha Salman

J. Appl. Phys. 113, 023302 (2013); http://dx.doi.org/10.1063/1.4774073 (8 pages)

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A new field emission model of carbon nanotubes (CNTs) to simulate gas detection mechanism in CNT based ionization gas sensor has been developed. The new model consists of three modules which are combined together and embedded in the standard particle-in-cell/Monte Carlo collision codes. The functionality of the enhanced model is checked by varying the gas pressure and gap spacing in the simulations. From the results, around one order of magnitude decrease in the breakdown voltages and two orders of magnitude faster response time is observed. The lowest breakdown voltages are observed when intertube spacing is equal to height of the nanotube. The field enhancement factor β is calculated from our model and compared with the β of the well established model. The closeness among the values of β validates the performance of our field emission model. Furthermore, the β of our model is compared with the β of the existing ionization gas sensors. It was found that the β of our sensor is around 3 times better than the β of the gold nanowire based ionization gas sensor and 28 times better than the β of the other CNT based ionization gas sensor. These results suggest that by properly controlling the growth of CNT structures, an optimized CNT based ionization gas sensor can be realized.
Show PACS
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.35.Kt Nanotube devices
FREE

Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

Ryan Comes, Man Gu, Mikhail Khokhlov, Hongxue Liu, Jiwei Lu, and Stuart A. Wolf

J. Appl. Phys. 113, 023303 (2013); http://dx.doi.org/10.1063/1.4774238 (7 pages) | Cited 2 times

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.
Show PACS
68.55.J- Morphology of films
75.70.Ak Magnetic properties of monolayers and thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.15.Fg Pulsed laser ablation deposition
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Experimental investigations on the relations between configurations and radiation patterns of a relativistic magnetron with diffraction output

Wei Li, Yong-gui Liu, Jun Zhang, Di-fu Shi, and Wei-qi Zhang

J. Appl. Phys. 113, 023304 (2013); http://dx.doi.org/10.1063/1.4774245 (4 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The relations between configurations of a relativistic magnetron with diffraction output (MDO) and radiation patterns obtained by experimental investigations are presented in this paper. A fluorescent lamps array is used to snap microwave patterns radiated from an A6 type MDO. Experimental results are well in agreement with computer simulations. Conclusions obtained from experiments are that (1) when an MDO operates at 2π mode, with all cavities tapered onto the output port, the MDO can directly radiate TE01 mode. (2) TEn1 (n > 0, n is integer) modes can be radiated from a π mode operating MDO with 2n azimuthally symmetric cavities tapered onto the output port. (3) By inserting optimal transition sections into tapered cavities, a pure TE11 microwave can be obtained.
Show PACS
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Direct current plasma jet at atmospheric pressure operating in nitrogen and air

X. L. Deng, A. Yu. Nikiforov, P. Vanraes, and Ch. Leys

J. Appl. Phys. 113, 023305 (2013); http://dx.doi.org/10.1063/1.4774328 (9 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An atmospheric pressure direct current (DC) plasma jet is investigated in N2 and dry air in terms of plasma properties and generation of active species in the active zone and the afterglow. The influence of working gases and the discharge current on plasma parameters and afterglow properties are studied. The electrical diagnostics show that discharge can be sustained in two different operating modes, depending on the current range: a self-pulsing regime at low current and a glow regime at high current. The gas temperature and the N2 vibrational temperature in the active zone of the jet and in the afterglow are determined by means of emission spectroscopy, based on fitting spectra of N2 second positive system (C3Π-B3Π) and the Boltzmann plot method, respectively. The spectra and temperature differences between the N2 and the air plasma jet are presented and analyzed. Space-resolved ozone and nitric oxide density measurements are carried out in the afterglow of the jet. The density of ozone, which is formed in the afterglow of nitrogen plasma jet, is quantitatively detected by an ozone monitor. The density of nitric oxide, which is generated only in the air plasma jet, is determined by means of mass-spectroscopy techniques.
Show PACS
52.25.Fi Transport properties
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements
52.75.-d Plasma devices
52.80.Hc Glow; corona

Energy distribution of electron flux at electrodes in a low pressure capacitively coupled plasma

Shahid Rauf, Leonid Dorf, Jason Kenney, and Ken Collins

J. Appl. Phys. 113, 023306 (2013); http://dx.doi.org/10.1063/1.4774306 (7 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A one-dimensional particle-in-cell (PIC) model is used to examine the energy distribution of electron flux at electrodes [labeled ge(ε,t), where ε is energy and t is time] in a low pressure 60 MHz capacitively coupled Ar discharge. The effect of gas pressure and an auxiliary DC voltage on ge(ε,t) is also investigated. It is found that the electrons only leave the plasma for a short time period during the radio-frequency (RF) cycle when the sheath collapses at the electrode. Furthermore, majority of the exiting electrons have energies below 10 eV with a distribution ge(ε,t) that is narrow in both energy and time. At relatively high pressures (≥4.67 Pa for the conditions considered), the relationship between the time-average distribution ge(ε) and electron temperature in the plasma (Te) can be easily established. Below 4.67 Pa, kinetic effects become important, making it difficult to interpret ge(ε) in terms of Te. At low pressures, ge(ε,t) is found to broaden in both energy and time except for a narrow pressure range around 1.2 Pa where the distribution narrows temporally. These low pressure kinetic phenomena are observed when the electrons can be accelerated by expanding sheaths to speeds that allow them to traverse the inter-electrode distance quickly (<1.5 RF cycles for conditions considered) and when electrons undergo few collisions during this excursion. The mean energy of exiting electrons increases with decreasing gas pressure, especially below 1.0 Pa, due to higher Te and secondary electrons retaining a larger fraction of the energy they gained during initial sheath acceleration. For the relatively small DC voltages examined (|Vdc|/Vrf ≤ 0.15), the application of a negative DC voltage on an electrode decreases the electron flux there but has a weak impact on the ge profile.
Show PACS
52.25.Fi Transport properties
52.40.Kh Plasma sheaths
52.65.Rr Particle-in-cell method
52.80.Pi High-frequency and RF discharges
52.20.Fs Electron collisions
52.25.Dg Plasma kinetic equations
back to top Structural, Mechanical, Thermodynamic, and Optical Properties of Condensed Matter

High Faraday effect of antiferromagnetic/ion-crystal photonic crystals in far infrared region

Xuan-Zhang Wang and Yan Zhao

J. Appl. Phys. 113, 023501 (2013); http://dx.doi.org/10.1063/1.4773476 (6 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The Faraday effect of one-dimensional antiferromagnetic/ion-crystal photonic crystals (AF/IC PCs) is investigated. In numerical calculation, AF layers are FeF2 and IC layers are of IV-VI semiconductor. A valuable geometry with higher Faraday effect is found, where an incident electromagnetic wave normally illuminates the lateral surface of such a PC and the external field and AF anisotropy axis both are pointed along the wave-vector. From the numerical results based on several relevant PCs, we conclude that the FeF2/PbSe PC possesses the highest Faraday effect. Although the effect originates from AF layers and is influenced by the PC anisotropy, the rotation angle is the largest at a finite AF filling ratio (fa = 0.6), reaching 22.5°μm−1 and about 20 times that of FeF2. We also discuss the wave attenuation in the PCs, and consequently find that the attenuation is lower and the transmission is better in this geometry.
Show PACS
78.20.Ls Magneto-optical effects
78.30.Hv Other nonmetallic inorganics
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
75.50.Ee Antiferromagnetics

CdSe colloidal nanocrystals monolithically integrated in a pseudomorphic semiconductor epilayer

Erick M. Larramendi, Oliver Schöps, Mikhail V. Artemyev, Detlef Schikora, Klaus Lischka, and Ulrike Woggon

J. Appl. Phys. 113, 023502 (2013); http://dx.doi.org/10.1063/1.4773531 (6 pages)

Online Publication Date: 8 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
As optically active emitters in a semiconductor matrix, core/shell and bare CdSe colloidal nanocrystals (CNCs) were monolithically incorporated in ZnSe pseudomorphic epilayers by molecular beam epitaxy (MBE). A suspension of wet chemically synthesized CNCs was sprayed ex-situ over a pseudomorphic ZnSe/GaAs(001) heterostructure using a nebulizer. Subsequently, the matrix material growth was resumed to form a capping layer by a slow MBE growth mode. Structural investigations show high crystalline quality and pseudomorphic epitaxial character of the whole hybrid CNC-matrix structure. The core/shell CNCs remain optically active following the embedding process. Their emission is blue shifted without a significant change on the spectral shape, and shows the same temperature dependence as that of the free exciton peak energy in zinc-blende CdSe at temperatures above 80 K. Our optical characterization of the samples showed that the embedded CNCs were stable and that the structure of the host was preserved. These results are encouraging for the fabrication of more complex optoelectronic devices based on CNCs.
Show PACS
81.16.Be Chemical synthesis methods
82.70.Dd Colloids
68.55.ag Semiconductors
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Anomalous phonon behavior of carbon nanotubes: First-order influence of external load

Amin Aghaei, Kaushik Dayal, and Ryan S. Elliott

J. Appl. Phys. 113, 023503 (2013); http://dx.doi.org/10.1063/1.4774077 (7 pages)

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
External loads typically have an indirect influence on phonon curves, i.e., they influence the phonon curves by changing the state about which linearization is performed. In this paper, we show that in nanotubes, the axial load has a direct first-order influence on the long-wavelength behavior of the transverse acoustic (TA) mode. In particular, when the tube is force-free, the TA mode frequencies vary quadratically with wave number and have curvature (second derivative) proportional to the square-root of the nanotube's bending stiffness. When the tube has non-zero external force, the TA mode frequencies vary linearly with wave number and have slope proportional to the square-root of the axial force. Therefore, the TA phonon curves—and associated transport properties—are not material properties but rather can be directly tuned by external loads. In addition, we show that the out-of-plane shear deformation does not contribute to this mode and the unusual properties of the TA mode are exclusively due to bending. Our calculations consist of 3 parts: First, we use a linear chain of atoms as an illustrative example that can be solved in close-form; second, we use our recently developed symmetry-adapted phonon analysis method to present direct numerical evidence; and finally, we present a simple mechanical model that captures the essential physics of the geometric nonlinearity in slender nanotubes that couples the axial load directly to the phonon curves. We also compute the density of states and show the significant effect of the external load.
Show PACS
63.22.Gh Nanotubes and nanowires
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.dq Other elastic constants
62.20.F- Deformation and plasticity
62.25.-g Mechanical properties of nanoscale systems

Carrier heating and electron-phonon energy exchange effects on nonlinear transport phenomena in semiconductor films

G. Gonzalez de la Cruz and Yu. G. Gurevich

J. Appl. Phys. 113, 023504 (2013); http://dx.doi.org/10.1063/1.4773345 (6 pages)

Online Publication Date: 9 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Theory of nonlinear size effects is developed in semiconductor films in the presence of an external dc electric field. The electron and phonon temperatures are calculated self-consistently with the electron-phonon energy interaction taken into account and its influence on the electron current density is considered. The temperature distributions are calculated using appropriate boundary conditions at the surfaces of the semiconductor film. It is shown that the electron and phonon temperatures depend on the electron-phonon coupling factor and the film thickness. Because the electrical conductivity is a function of the electron and phonon temperature distributions, the electron current density in the semiconductor film becomes nonlinear as a function of the heating electric field. We discuss the nonlinear effects for different special cases.
Show PACS
66.70.Df Metals, alloys, and semiconductors
68.55.jd Thickness
71.70.Gm Exchange interactions
73.61.Ey III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments
63.20.kd Phonon-electron interactions

Mechanical properties and scaling laws of nanoporous gold

Xiao-Yu Sun, Guang-Kui Xu, Xiaoyan Li, Xi-Qiao Feng, and Huajian Gao

J. Appl. Phys. 113, 023505 (2013); http://dx.doi.org/10.1063/1.4774246 (9 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nanoporous metals are a class of novel nanomaterials with potential applications in many fields such as sensing, catalysis, and fuel cells. The present paper is aimed to investigate atomic mechanisms associated with the uniaxial tensile deformation behavior of nanoporous gold. A phase field method is adopted to generate the bicontinuous open-cell porous microstructure of the material. Molecular dynamics simulations then reveal that the uniaxial tensile deformation in such porous materials is accompanied by an accumulation of stacking faults in ligaments along the loading direction and their junctions with neighboring ligaments, as well as the formation of Lomer–Cottrell locks at such junctions. The tensile strain leads to progressive necking and rupture of some ligaments, ultimately resulting in failure of the material. The simulation results also suggest scaling laws for the effective Young's modulus, yield stress, and ultimate strength as functions of the relative mass density and average ligament size in the material.
Show PACS
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.de Elastic moduli
62.20.fg Shape-memory effect; yield stress; superelasticity
62.20.fq Plasticity and superplasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Effects of lateral overgrowth on residual strain and In incorporation in a-plane InGaN/GaN quantum wells on r-sapphire substrates

Moon-Taek Hong, Tae-Soo Kim, Ki-Nam Park, Sukkoo Jung, Younghak Chang, Gyu-Hyun Bang, Hyung-Gu Kim, Jina Jeon, Yoon-Ho Choi, Sung-Min Hwang, and Jung-Hoon Song

J. Appl. Phys. 113, 023506 (2013); http://dx.doi.org/10.1063/1.4774302 (4 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigated the effects of the patterned lateral over-growth on the residual strain in GaN templates and In incorporation in a-plane InGaN/GaN quantum wells grown on a r-sapphire substrate, by utilizing micro-photoluminescence and Raman scattering spectroscopy. Strong enhancement of emission intensity is observed from the wing area. We report a reduction in the residual strain and different In incorporation in the wing area. The InGaN quantum wells on the merged area have higher In composition with smaller residual strain of the GaN layers underneath.
Show PACS
68.65.Fg Quantum wells
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.07.St Quantum wells
68.55.ag Semiconductors

An experimental study on SrB4O7:Sm2+ as a pressure sensor

Qiumin Jing, Qiang Wu, Lei Liu, Ji-an Xu, Yan Bi, Yonggang Liu, Haihua Chen, Shenggang Liu, Yi Zhang, Lun Xiong, Yanchun Li, and Jing Liu

J. Appl. Phys. 113, 023507 (2013); http://dx.doi.org/10.1063/1.4774113 (5 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A pressure sensor of SrB4O7:Sm2+ has been synthesized and the pressure shift of its 7D0-5F0 fluorescence line has been recalibrated at room temperature up to 48 GPa and 127 GPa hydrostatically and non-hydrostatically, respectively. Different from previous study, our results show that the calibrated relation in the quasi-hydrostatic pressure environment is quite different from that in the non-hydrostatic pressure environment. The yield strength of SrB4O7:Sm2+ as a function of the pressure has been determined by the pressure gradient method in a diamond anvil cell. The results show that the yield strength of SrB4O7:Sm2+ increases from 2.85 GPa at a pressure of 7.9 GPa to 4.22 GPa at 25.4 GPa and is much smaller than that of ruby. The relatively small high-pressure yield strength of SrB4O7:Sm2+ is at the same level of the most sample materials. This would result in a small pressure difference with the coexisting sample, thus lead to a small error in the pressure measurement. The smaller yield strength and excellent fluorescent spectral characters of SrB4O7:Sm2+ make it a good substitute for ruby as a pressure scale in high-pressure experiments, especially under non-hydrostatic pressure environments.
Show PACS
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Incoherent twin boundary migration induced by ion irradiation in Cu

N. Li, J. Wang, Y. Q. Wang, Y. Serruys, M. Nastasi, and A. Misra

J. Appl. Phys. 113, 023508 (2013); http://dx.doi.org/10.1063/1.4774242 (8 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Grain boundaries can act as sinks for radiation-induced point defects. The sink capability is dependent on the atomic structures and varies with the type of point defects. Using high-resolution transmission electron microscopy, we observed that Σ3{112} incoherent twin boundary (ITB) in Cu films migrates under Cu3+ ion irradiation. Using atomistic modeling, we found that Σ3{112} ITB has the preferred sites for adsorbing interstitials and the preferential diffusion channels along the Shockley partial dislocations. Coupling with the high mobility of grain boundary Shockley dislocations within Σ3{112} ITB, we infer that Σ3{112} ITB migrates through the collective glide of grain boundary Shockley dislocations, driven by a concurrent reduction in the density of radiation-induced defects, which is demonstrated by the distribution of nearby radiation-induced defects.
Show PACS
61.72.Mm Grain and twin boundaries
61.80.Jh Ion radiation effects
68.55.-a Thin film structure and morphology
61.72.jj Interstitials
66.30.J- Diffusion of impurities

Influence of transparent coating hardness on laser-generated ultrasonic waves

Yuning Guo, Dexing Yang, Wen Feng, and Ying Chang

J. Appl. Phys. 113, 023509 (2013); http://dx.doi.org/10.1063/1.4773533 (6 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Numerical models are established to investigate the influence of transparent coating hardness on the laser-generated thermoelastic force source and ultrasonic waves in coating-substrate systems by using finite element method. With the increase of coating hardness, the characteristic of longitudinal wave in substrate is more obvious due to the gradual increase of reactive force produced by coating constraint; the directivity patterns of longitudinal wave show that the energy concentration area transfers from bilateral area to the axial direction area gradually. Therefore, the directivity pattern can be regulated to obtain the better ultrasonic signals by coating different hardness materials. It is significant for further development of the experiment in composite evaluation and in extreme condition.
Show PACS
62.65.+k Acoustical properties of solids
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.D- Elasticity
62.20.Qp Friction, tribology, and hardness

Influence of stress on structural properties of AlGaN/GaN high electron mobility transistor layers grown on 150 mm diameter Si (111) substrate

H. F. Liu, S. B. Dolmanan, L. Zhang, S. J. Chua, D. Z. Chi, M. Heuken, and S. Tripathy

J. Appl. Phys. 113, 023510 (2013); http://dx.doi.org/10.1063/1.4774288 (7 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Effects of stress imposed by individual nitride layers on structural properties of an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure, which was grown on a 150 mm diameter Si (111) substrate by metal-organic chemical vapor deposition employing high-temperature step-graded AlxGa1−xN/AlN buffer layers, were studied using transmission electron microscopy, visible micro-Raman spectroscopy, and high-resolution x-ray diffraction. It is revealed that all the nitride layers are more or less tensile strained on the Si (111) substrate; however, strain relaxations occurred at all the heterointerfaces except for the AlGaN/(AlN/)GaN two-dimensional electron gas interface, which is desired for achieving high performance HEMT. The wafer curvature, an important parameter for large area epitaxy of GaN-on-Si, is modeled on the basis of stress distribution within individual layers of the multilayered AlGaN/GaN HEMT structure via the close-form expression developed by Olsen and Ettenberg [J. Appl. Phys. 48, 2543 (1977)]. The evolution of wafer curvature induced by substrate thinning and stress redistribution is predicted by this model, which is further qualitatively confirmed by experimental results.
Show PACS
85.30.Tv Field effect devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Evaluation of Sr2MMoO6 (M = Mg, Mn) as anode materials in solid-oxide fuel cells: A neutron diffraction study

L. Troncoso, M. J. Martínez-Lope, J. A. Alonso, and M. T. Fernández-Díaz

J. Appl. Phys. 113, 023511 (2013); http://dx.doi.org/10.1063/1.4774764 (8 pages)

Online Publication Date: 10 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Sr2MMoO6 (M = Mg, Mn) double perovskites have recently been proposed as anode materials in solid-oxide fuel cells (SOFC). The evolution of their crystal structures has been followed by “in situ” temperature-dependent neutron powder diffraction from 25 °C room temperature (RT) to 930 °C by heating in ultrahigh vacuum (PO2 ≈ 10−6 Torr) in order to simulate the reducing atmosphere corresponding to the working conditions of an anode in a SOFC. At RT, the samples are described as tetragonal (I4/m space group) and monoclinic (P21/n) for M = Mg, Mn, respectively. Sr2MgMoO6 undergoes a structural phase transition from tetragonal to cubic (Fm-3m) below 300 °C; Sr2MnMoO6 experiences two consecutive phase transitions to tetragonal (I4/m) and finally cubic (Fm-3m) at 600 °C and above. In the cubic phases, the absence of octahedral tilting accounts for a good overlap between the oxygen and transition-metal orbitals, resulting in a good electronic conductivity; a high mobility of the oxygen atoms is derived from the elevated displacement parameters, for instance 3.0 Å2 and 4.6 Å2 at 930 °C for M = Mg, Mn, respectively. Both factors contribute to the excellent performance described for these mixed ionic and electronic conductor oxides as anodes in single fuel cells. From dilatometric measurements, the thermal expansion coefficients (TEC) in the cubic region are 12.7 × 10−6 K−1 and 13.0 × 10−6 K−1 for M = Mg and Mn, respectively. These figures are comparable to those obtained from the mentioned structural analysis; moreover, the TECs for the cubic phases perfectly match those of the usual electrolytes in a SOFC.
Show PACS
61.66.Fn Inorganic compounds
65.40.De Thermal expansion; thermomechanical effects
72.80.Sk Insulators
82.45.Fk Electrodes
64.70.K- Solid-solid transitions

On the interplay of point defects and Cd in non-polar ZnCdO films

A. Zubiaga, F. Reurings, F. Tuomisto, F. Plazaola, J. A. García, A. Yu. Kuznetsov, W. Egger, J. Zúñiga-Pérez, and V. Muñoz-Sanjosé

J. Appl. Phys. 113, 023512 (2013); http://dx.doi.org/10.1063/1.4775396 (7 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Non-polar ZnCdO films, grown over m- and r-sapphire with a Cd concentration ranging between 0.8% and 5%, have been studied by means of slow positron annihilation spectroscopy (PAS) combined with chemical depth profiling by secondary ion mass spectroscopy and Rutherford back-scattering. Vacancy clusters and Zn vacancies with concentrations up to 1017 cm−3 and 1018 cm−3, respectively, have been measured inside the films. Secondary ion mass spectroscopy results show that most Cd stays inside the ZnCdO film but the diffused atoms can penetrate up to 1.3 μm inside the ZnO buffer. PAS results give an insight to the structure of the meta-stable ZnCdO above the thermodynamical solubility limit of 2%. A correlation between the concentration of vacancy clusters and Cd has been measured. The concentration of Zn vacancies is one order of magnitude larger than in as-grown non-polar ZnO films and the vacancy cluster are, at least partly, created by the aggregation of smaller Zn vacancy related defects. The Zn vacancy related defects and the vacancy clusters accumulate around the Cd atoms as a way to release the strain induced by the substitutional CdZn in the ZnO crystal.
Show PACS
61.72.jd Vacancies
61.72.sd Impurity concentration
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.70.Bj Positron annihilation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Radiation damage in heteroepitaxial BaTiO3 thin films on SrTiO3 under Ne ion irradiation

Z. Bi, B. P. Uberuaga, L. J. Vernon, E. Fu, Y. Wang, N. Li, H. Wang, A. Misra, and Q. X. Jia

J. Appl. Phys. 113, 023513 (2013); http://dx.doi.org/10.1063/1.4775495 (8 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The microstructure evolution of heteroepitaxial BaTiO3 (BTO) thin films grown on single crystal (001) SrTiO3 (STO) under Ne irradiation at room temperature was systematically investigated with special attention given to the behavior at the BTO/STO interface. Cross sectional transmission electron microscope investigations reveal that amorphization occurs at the top BTO film region. BTO grains in the dimensions of 10–20 nm survived the irradiation damage and maintained their original crystal orientation. Other irradiation-induced defects such as dislocation loops and defect clusters were observed only at the portion of the BTO thin film near the interface, but not at the STO side of the bilayer. Atomic calculations find that the energetics of defects are very similar on each side of the BTO/STO interface, suggesting that the interface will not significantly modify radiation damage evolution in this system, in agreement with the experimental observations. These results support the hypothesis we presented in previous work about the role of coherent interfaces on radiation damage evolution.
Show PACS
61.80.Jh Ion radiation effects
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Dopant mapping in highly p-doped silicon by micro-Raman spectroscopy at various injection levels

T. Kunz, M. T. Hessmann, S. Seren, B. Meidel, B. Terheiden, and C. J. Brabec

J. Appl. Phys. 113, 023514 (2013); http://dx.doi.org/10.1063/1.4773110 (8 pages)

Online Publication Date: 11 January 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Micro-Raman spectroscopy has been used to investigate the acceptor distribution in highly p-doped silicon. As an example, the dopant distribution in crystalline thin-film layers, as developed for solar cells, was mapped. The method is based on the analysis of the Fano-type Raman peak shape which is caused by free charge carriers. For calibration of the Raman acceptor measurements (excitation at a wavelength of 532 nm), we used mono-crystalline reference samples whose acceptor concentration was determined by electrochemical capacitance voltage. We find a significant influence of light induced free charge carriers on the peak shape which results from typical Raman excitation. Thus, the selection of a suitable intensity is important to avoid a too low signal-to-noise ratio on the one hand and systematic errors due to light induced carriers on the other hand. Different evaluation methods, i.e., peak asymmetry versus peak width analysis, are compared in respect to interference caused by random noise of the spectra or else by internal stress in the sample. While the width analysis method is more robust to a low signal-to-noise ratio, the symmetry analysis is more reliable in case of high intrinsic stress.
Show PACS
81.05.Cy Elemental semiconductors
61.72.sh Impurity distribution
61.72.uf Ge and Si
88.40.jj Silicon solar cells
71.55.Cn Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
Page 1 of 5 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close