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

15 Oct 2005

Volume 98, Issue 8, Articles (08xxxx)

Return to All Sections
back to top
RSS Feeds

Photoluminescence properties of quasialigned ZnCdO nanorods

F. Z. Wang, H. P. He, Z. Z. Ye, and L. P. Zhu

J. Appl. Phys. 98, 084301 (2005); http://dx.doi.org/10.1063/1.2089164 (4 pages) | Cited 17 times

Online Publication Date: 18 October 2005

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
We report on the photoluminescence (PL) properties of quasialigned ZnCdO single-crystal nanorods prepared by thermal evaporation of Zn and CdCl2 on a Si substrate using Au as a catalyst. The temperature-dependent PL spectra of the ZnCdO nanorods show that each spectrum displays an intense near-band-edge (NBE) emission around 3.1 eV, as well as a weak defect-related band around 2.5 eV. At low temperatures, the NBE band consists of three peaks at 3.23, 3.16, and 3.06 eV. From time-integrated and time-resolved PL analyses, we suggest that the peak at 3.06 eV is associated with carriers localized at potential minima induced by the Cd spatial inhomogeneous distribution in ZnCdO alloys. The peak at 3.16 eV is attributed to the excitonic emission of ZnCdO, while the peak at 3.23 eV is ascribed to bound excitons in ZnO.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
71.55.Gs II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.35.-y Excitons and related phenomena

Morphology evolution and local electric properties of Au nanoparticles on ZnO thin films

E. György, J. Santiso, A. Figueras, A. Giannoudakos, M. Kompitsas, and I. N. Mihailescu

J. Appl. Phys. 98, 084302 (2005); http://dx.doi.org/10.1063/1.2089166 (4 pages) | Cited 3 times

Online Publication Date: 18 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the sequential two-step pulsed laser deposition of nanostructures consisting of ZnO thin films covered with Au nanoparticles. Zn and Au targets were alternatively submitted to pulses generated by a frequency tripled Nd:yttrium aluminium garnet (λ = 355 nm, τ ∼ 10 ns, ν = 10 Hz) laser. The ZnO films were synthesized in 20 Pa oxygen pressure, whereas the subsequent Au coverage was applied in vacuum. The dynamics of Au nanoparticles grown on the ZnO thin-films surface was studied by atomic force microscopy as a function of number of laser pulses applied for the ablation of the Au target. The nanoparticle diameters increase with the number of laser pulses while their height decreases. The local electric properties of the uncoated (reference) and coated with Au ZnO thin films was investigated by current sensing mode atomic force microscopy.
Show PACS
81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
81.16.Mk Laser-assisted deposition
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
73.61.Ga II-VI semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Fg Semiconductor surfaces
61.46.-w Structure of nanoscale materials

Equilibrium magnetic moment configurations in magnetic nanoparticle films: Effects of anisotropy, dipolar interaction, and Zeeman energy

C. Xu, Y. Q. Ma, and P. M. Hui

J. Appl. Phys. 98, 084303 (2005); http://dx.doi.org/10.1063/1.2103413 (8 pages) | Cited 2 times

Online Publication Date: 19 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The equilibrium configurations of films consisting of magnetic small particles in which the anisotropy energy tends to align the magnetic moments perpendicular to the film are studied by Monte Carlo simulations. The effects of anisotropy energy, dipolar interaction, and Zeeman energy due to an external applied magnetic field, which can either be perpendicular or parallel to the film, are considered. As the relative strength of the relevant interaction energies changes, the system exhibits a variety of different magnetic moment configurations. Due to the competition between the dipolar interaction energy and the anisotropy energy, it is found that an approximately antiferromagnetic alignment with moments oriented perpendicular to the film results when the anisotropy energy dominates; while an in-plane antiferromagnetic alignment results when the dipolar interaction energy dominates. Results obtained by a zero-temperature analysis based on energy minimization are found to be in qualitative agreement with results obtained by numerical simulations.
Show PACS
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Cr Saturation moments and magnetic susceptibilities
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Ee Antiferromagnetics
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects

Control of the plasmon absorption of gold nanoparticles with a two-color excitation

I. V. Kityk, K. J. Plucinski, J. Ebothé, A. Ali Umar, and M. Oyama

J. Appl. Phys. 98, 084304 (2005); http://dx.doi.org/10.1063/1.2103409 (4 pages) | Cited 6 times

Online Publication Date: 20 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Substantial photoinduced changes of ultraviolet (UV) -visible (UV-vis) optical spectra were observed for the Au nanoparticles prepared by a “touch” seed-mediated growth technique on the surface of indium-tin-oxide substrate. The phototreatment was performed by two-color coherent laser beams with a wavelength of 1060 nm (fundamental beam) and double frequency 530 nm (writing beam). The maximal photoinduced changes of the UV-vis spectra were observed for the surfaces possessing low resistivity (about 4 Ω/sq). Those of higher resistivity (about 50 Ω/sq) demonstrate only slight shifts of the main Au particle surface-plasmon resonance maxima at λ = 570 nm. The effect observed is a consequence of a superposition of optically induced surface plasmon resonance, scattering on optically induced grating and electron-phonon relaxation.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.40.Kc Metals, semimetals, and alloys
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.22.Lp Collective excitations
73.25.+i Surface conductivity and carrier phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Thermal quenching of luminescence from buried and surface InGaAs self-assembled quantum dots with high sheet density

Z. F. Wei, S. J. Xu, R. F. Duan, Q. Li, Jian Wang, Y. P. Zeng, and H. C. Liu

J. Appl. Phys. 98, 084305 (2005); http://dx.doi.org/10.1063/1.2112176 (4 pages) | Cited 12 times

Online Publication Date: 20 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Variable-temperature photoluminescence (PL) spectra of Si-doped self-assembled InGaAs quantum dots (QDs) with and without GaAs cap layers were measured. Narrow and strong emission peak at 1075 nm and broad and weak peak at 1310 nm were observed for the buried and surface QDs at low temperature, respectively. As large as 210 meV redshift of the PL peak of the surface QDs with respect to that of the buried QDs is mainly due to the change of the strain around QDs before and after growth of the GaAs cap layer. Using the developed localized-state luminescence model, we quantitatively calculate the temperature dependence of PL peaks and integrated intensities of the two samples. The results reveal that there exists a large difference in microscopic mechanisms of PL thermal quenching between two samples.
Show PACS
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

Electrically aligned binary system of nanoparticles

B. N. Pal, S. Basu, and D. Chakravorty

J. Appl. Phys. 98, 084306 (2005); http://dx.doi.org/10.1063/1.2106012 (5 pages)

Online Publication Date: 21 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Aligned arrays of binary nanoparticles of silver and silver oxide, respectively, with mean diameters of 8.5 nm have been prepared within a polymethylmethacrylate film. The alignment along an electric-field direction has been achieved by applying an electric field of ∼ 10 V/mm at frequency ranging from 1 kHz to 1 MHz. This behavior has been explained as arising due to a dipole-dipole interaction between the metal and oxide nanoparticles, respectively. The electrical resistivity is shown to arise due to variable range hopping mechanism. These nanocomposites exhibit three orders of magnitude resistivity changes as the relative humidity is varied from 35% to 95%.
Show PACS
81.05.Qk Reinforced polymers and polymer-based composites
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
73.61.-r Electrical properties of specific thin films

Electron microscopy and photoelectron spectromicroscopy study of catalyst-free transformation of carbon nanoparticles into nanotubes

S. Botti, R. Ciardi, F. Fabbri, R. Larciprete, A. Goldoni, L. Gregoratti, B. Kaulich, and M. Kiskinova

J. Appl. Phys. 98, 084307 (2005); http://dx.doi.org/10.1063/1.2077848 (6 pages) | Cited 3 times

Online Publication Date: 21 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The reorganization of the morphologically complex amorphous carbon nanoparticle layers deposited on a Si substrate into ordered sp2 entities was investigated by means of two complementary techniques, synchrotron radiation x-ray photoelectron microscopy and scanning electron microscopy, which provided the necessary chemical and structural information at submicrometer length scales. The studies were focused on the effect of the local thickness of the carbon nanoparticle layer on the extent of the restructuring process. The lateral distribution of the phases formed on the surface and their local chemical configuration were revealed by measuring C 1s and the Si 2p core level spectra with photoelectron spectromicroscopy. The results showed that an effective graphitization, which on the basis of complementary characterization techniques was associated to the formation of single-wall nanotubes, occurs only in areas with a high density of nanoparticles. These findings indicate that tube self-assembling is promoted by the interaction between neighboring nanoparticles.
Show PACS
61.46.-w Structure of nanoscale materials
68.55.A- Nucleation and growth
68.37.Yz X-ray microscopy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Nonlinear I-V characteristics of nanotransistors in the Landauer-Büttiker formalism

G. A. Nemnes, U. Wulf, and P. N. Racec

J. Appl. Phys. 98, 084308 (2005); http://dx.doi.org/10.1063/1.2113413 (8 pages) | Cited 5 times

Online Publication Date: 21 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present the nonlinear I-V characteristics of a nanoscale metal-oxide-semiconductor field-effect transistor in the Landauer-Büttiker formalism. In our three-dimensional ballistic model the gate, source, and drain contacts are treated on an equal footing. As in the drift-diffusion regime for ballistic transport a saturation of the drain current results. We demonstrate the quantum mechanism for the ballistic drain current saturation. As a specific signature of ballistic transport we find a specific threshold characteristic with a close-to-linear dependence of the drain current on the drain voltage. This threshold characteristic separates the ON-state regime from a quasi-OFF-state regime in which the device works as a tunneling transistor. Long- and short-channel effects are analyzed in both regimes and compared qualitatively with existing experimental data by Intel [ B. Doyle et al., Intel Technol. J. 6, 42 (2002) ].
Show PACS
85.30.Tv Field effect devices
85.35.-p Nanoelectronic devices
73.23.Ad Ballistic transport
73.63.-b Electronic transport in nanoscale materials and structures
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Gk Tunneling
66.30.-h Diffusion in solids
85.30.De Semiconductor-device characterization, design, and modeling

Surface-plasmon resonance of Ag nanoparticles in polyimide

Sung K. Lim, Keum J. Chung, C. K. Kim, Dong W. Shin, Young-Ho Kim, and Chong S. Yoon

J. Appl. Phys. 98, 084309 (2005); http://dx.doi.org/10.1063/1.2106019 (4 pages) | Cited 18 times

Online Publication Date: 24 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ag nanoparticles were fabricated by sandwiching a Ag thin film (2.5–15 nm thick) between two polyimide precursor layers. During imidization, depending on the initial Ag film thickness, 10–20 nm sized Ag nanoparticles arranged in a monolayer were formed within the polymer matrix. The Ag particles exhibited a pronounced localized surface-plasmon resonance effect. The resonance wavelength (460–540 nm) can be easily tuned by ±40 nm by simply changing the Ag film thickness which alters the mean particle diameter. The classical Mie model was introduced to explain the size dependence of the plasmon peaks.
Show PACS
81.07.Bc Nanocrystalline materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials

Nanoscale potential distribution across multiquantum well structures: Kelvin probe force microscopy and secondary electron imaging

A. Schwarzman, E. Grunbaum, E. Strassburg, E. Lepkifker, A. Boag, Y. Rosenwaks, Th. Glatzel, Z. Barkay, M. Mazzer, and K. Barnham

J. Appl. Phys. 98, 084310 (2005); http://dx.doi.org/10.1063/1.2106011 (4 pages) | Cited 10 times

Online Publication Date: 24 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ultrahigh vacuum cross-sectional Kelvin probe force microscopy has been used to characterize In0.17GaAs/GaAsP0.06 multiquantum well structures, together with secondary electron microscopy. Individual 8 nm quantum wells were well resolved in both methods, and were found to be in a good agreement with numerical simulations of the work function profile. It is shown that the surface potential contrast in the Kelvin probe force microscopy measurements is greatly enhanced using deconvolution algorithms, and the reasons for the different contrast in the electron microscopy images are discussed.
Show PACS
68.65.Fg Quantum wells
68.37.Ps Atomic force microscopy (AFM)

Determining a complete three-dimensional set of eigenfunctions for nanoscale structure analysis

Dennis M. Sullivan

J. Appl. Phys. 98, 084311 (2005); http://dx.doi.org/10.1063/1.2108157 (9 pages) | Cited 3 times

Online Publication Date: 25 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
With the shrinking dimensions of semiconductor devices, it is becoming increasingly important that the analysis of devices be rooted in quantum mechanics rather than in classical analysis. The starting point in the analysis of structures is the determination of the quantum eigenenergies and the corresponding eigenfunctions. It is particularly desirable to determine a complete set of eigenfunctions as a basis for any quantum analysis. A method based on the finite-difference time-domain formulation is presented that systematically determines an orthonormal basis of eigenstates for submicron structures.
Show PACS
85.30.De Semiconductor-device characterization, design, and modeling

Evaluation of insulator thickness through excitation-wavelength dependence of photoluminescence of CdSe/ZnS nanocrystals

Kazunari Ozasa, Shigeyuki Nemoto, Mizuo Maeda, and Masahiko Hara

J. Appl. Phys. 98, 084312 (2005); http://dx.doi.org/10.1063/1.2108149 (5 pages) | Cited 3 times

Online Publication Date: 25 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have observed that the photoluminescence (PL) intensity for CdSe/ZnS nanocrystals (NCs) placed on insulator films depends on excitation wavelength and insulator thickness, and thus the visualization and thickness evaluation of insulator patterns can be achieved by the PL measurement of CdSe/ZnS NCs. On the basis of the multireflection/interference calculation, the change of the PL intensity according to the thickness/wavelength is attributed to the interference of excitation light. The evaluation of the thickness profile of the insulator pattern is demonstrated for GaAs-oxide ring patterns formed by solution etching of GaAs. The advantages of the thickness evaluation through the PL of CdSe/ZnS NCs are simplicity in measurement and horizontal resolution up to 10 nm.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
61.46.-w Structure of nanoscale materials

Field-emission characteristics of carbon nanotube paste layers

Tae Sik Oh, Ji Beom Yoo, Chong Yun Park, Seong Eui Lee, Jeong Hee Lee, and Jong Min Kim

J. Appl. Phys. 98, 084313 (2005); http://dx.doi.org/10.1063/1.2103412 (9 pages) | Cited 6 times

Online Publication Date: 26 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A three-dimensional simulator was used to analyze the field-emission mechanism of a carbon nanotube (CNT) emitter layer as a surface electron emitter in a triode structure for field-emission display. An electrostatic image potential was added to the Fowler-Nordheim equation to improve the accuracy of the calculation, and then several important parameters affecting the field-emission characteristics were studied. We calculated the field enhancement factor (β) and emission factor (κ) of the CNT emitter layer using the experimentally obtained current-voltage (I-V) values and the extended Fowler-Nordheim equation by the least-squares-fitting method. By simulating 211 structures, we confirmed the existence of a shielding effect between the emitters and a penetration phenomenon of the anode voltage.
Show PACS
79.70.+q Field emission, ionization, evaporation, and desorption
85.45.Db Field emitters and arrays, cold electron emitters

Near-infrared photoconductive and photovoltaic devices using single-wall carbon nanotubes in conductive polymer films

S. Kazaoui, N. Minami, B. Nalini, Y. Kim, and K. Hara

J. Appl. Phys. 98, 084314 (2005); http://dx.doi.org/10.1063/1.2113419 (6 pages) | Cited 29 times

Online Publication Date: 26 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have fabricated prototypical Al/single-wall carbon nanotube (SWNT)-polymer/indium tin oxide thin-film devices that exhibit promising photoconductive and photovoltaic responses in a broad spectral range, typically from 300 to 1600 nm. This achievement was made possible by finely dispersed SWNT powders in polymer matrices such as poly-phenylene-vinylene and poly-thiophene. These devices utilize (i) the intrinsic near-infrared light harvesting properties of semiconducting SWNTs, (ii) the electronic transport properties of both semiconducting and metallic SWNTs in combination with those of the polymer matrices, and (iii) probably charge/energy transfer processes between SWNTs and the polymers. By selecting different sources of SWNTs and polymers, we have shown that the optoelectronic properties of these devices are potentially tunable. To support our investigation, several techniques including spectrally resolved photoconductivity, optical absorption, and photoluminescence spectroscopy were utilized.
Show PACS
85.35.Kt Nanotube devices
85.60.-q Optoelectronic devices

DNA linker controlled single electron tunneling behavior of nanoparticle assembly

Jae-Hyun Lee, Jinwoo Cheon, Sun Bae Lee, Young-Wook Chang, Sung-In Kim, and Kyung-Hwa Yoo

J. Appl. Phys. 98, 084315 (2005); http://dx.doi.org/10.1063/1.2103411 (3 pages) | Cited 3 times

Online Publication Date: 27 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report an efficient method for the fabrication of a single electron transistor (SET) using DNA-assisted assembly of nanoparticles. In this method, the DNA molecules function not only as the assembler, but also as the modulator for the electron tunneling behaviors of single electron transistors. A study of the assembly between an Au nanoparticle ( ∼ 10 nm) and various lengths of DNA molecules confirms the effectiveness of this method in creating a SET. Most devices exhibited clear single electron effects.
Show PACS
85.35.Gv Single electron devices

Study of laser-induced self-oscillations in silicon nanomechanical resonators

Jingjing Li and S. Evoy

J. Appl. Phys. 98, 084316 (2005); http://dx.doi.org/10.1063/1.2099513 (5 pages) | Cited 1 time

Online Publication Date: 28 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a study of laser-induced oscillation of nanomechanical resonators. The modes of motion of single-stage and double-stage paddle resonators are first assessed using finite element analysis and experimentally observed using piezoelectric actuation of the devices. The flexural modes of the same devices are then excited at resonance using laser-induced thermal effects. As the actuating power is gradually increased, the resonators experience three phases of resonance characterized by distinct changes of amplitude and number of peaks observed. In addition, the resonant frequencies initially show a steady decrease with actuating power followed by a distinct increase. Finally, a sharpening of the resonant response is also observed as actuating power is increased. However, such peak sharpening is also accompanied by instabilities of the center frequency. These instabilities could be induced by a frequency mismatch between the parametric actuation mechanism and the natural resonance of the device, or by optically induced temperature fluctuations along the length of the resonator supports.
Show PACS
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Assessment of the attained temperatures and of melting in the nanosecond irradiation of doped poly(methylmethylacrylate) at 308, 248, and 193 nm via the examination of dopant reactivity

Giannis Bounos, Andreas Kolloch, Taxiarhos Stergiannakos, Erene Varatsikou, and Savas Georgiou

J. Appl. Phys. 98, 084317 (2005); http://dx.doi.org/10.1063/1.2076430 (9 pages) | Cited 5 times

Online Publication Date: 28 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The thermal and structural changes effected to poly(methylmethylacrylate) (PMMA) upon irradiation at 308, 248, and 193 nm are assessed via the examination of the formation yields of the products formed by the photolysis of iodoaromatics (iodonaphthalene and iodophenanthrene–ArI–) dopants. Specifically, the main aryl product, the hydrogen-substituted derivative ArH, is formed via a thermally activated process (hydrogen-atom abstraction); thus, its formation efficiency reflects the temperature evolution in the substrate following UV irradiation. In the case of iodonaphthalene dopant, biaryl species (1,1-binaphthalene and perylene) are also formed via diffusion-limited reaction of the aryl radicals; thus, their yield reflects the extent of polymer melting. To this end, laser-induced fluorescence is employed for the quantification of the aryl products formed in the substrate as a function of the irradiation fluence. At all wavelengths, the ArH amount scales linearly with Flaser at low fluences, but at higher fluences, it increases sharply reaching a plateau near the ablation threshold. Only quantitative differences concerning the fluence onset of the ArH increase and the amount of product remaining in the substrate are observed. Simulations accounting for the temporal and spatial evolutions of the temperature reproduce well the observed Flaser dependences. The quantitative differences in the extent of ArH formation are well accounted by the extent of the heat diffusion to the sublayers. Thus, contrary to many previous suggestions, a thermal process is demonstrated to be dominant at the three wavelengths. Concerning the biaryl species, their yield decreases from 308 to 193 nm. The simulation of their formation yield provides semiquantitative information about the polymer viscosity changes (melting) upon irradiation at the three wavelengths. Besides the mechanistic implications, the study also provides insight into the factors affecting the extent of chemical modifications in laser processing of polymers and organic substrates in general. In particular, the reduced extent of chemical modifications upon ablation at strongly absorbed wavelengths is indicated to be crucial for the success of these procedures.
Show PACS
61.82.Pv Polymers, organic compounds
61.25.H- Macromolecular and polymers solutions; polymer melts
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
66.20.-d Viscosity of liquids; diffusive momentum transport
64.70.D- Solid-liquid transitions

Magnetization reversal in diamond-shaped pseudo-spin-valve nanomagnets

S. Goolaup, A. O. Adeyeye, and N. Singh

J. Appl. Phys. 98, 084318 (2005); http://dx.doi.org/10.1063/1.2108150 (8 pages) | Cited 2 times

Online Publication Date: 28 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A systematic investigation of the magnetization reversal process of diamond-shaped Ni80Fe20(10 nm)/Cu(tCu nm)/Ni80Fe20(40 nm) pseudo-spin-valve nanostructures is presented. The structures were fabricated on silicon substrate using deep ultraviolet lithography at 248 nm exposing wavelength. By carefully selecting two ferromagnetic layer thicknesses, with different reversal mechanisms, we have created a magnetic structure with unique magnetic properties. We observed that the magnetization reversal process of the spin valve is strongly influenced by the Cu spacer layer thickness. Our experimental results were substantiated with a three-dimensional micromagnetic simulation.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Jk Magnetization reversal mechanisms
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials

Optical-geometrical effects on the photoluminescence spectra of Si nanocrystals embedded in SiO2

R. Ferre, B. Garrido, P. Pellegrino, M. Perálvarez, C. García, J. A. Moreno, J. Carreras, and J. R. Morante

J. Appl. Phys. 98, 084319 (2005); http://dx.doi.org/10.1063/1.2115100 (7 pages) | Cited 5 times

Online Publication Date: 31 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrate that thickness, optical constants, and details of the multilayer stack, together with the detection setting, strongly influence the photoluminescence spectra of Si nanocrystals embedded in SiO2. Due to multiple reflections of the visible light against the opaque silicon substrate, an interference pattern is built inside the oxide layer, which is responsible for the modifications in the measured spectra. This interference effect is complicated by the depth dependence of (i) the intensity of the excitation laser and (ii) the concentration of the emitting nanocrystals. These variations can give rise to apparent features in the recorded spectra, such as peak shifts, satellite shoulders, and even splittings, which can be mistaken as intrinsic material features. Thus, they can give rise to an erroneous attribution of optical bands or estimate of the average particle size, while they are only optical-geometrical artifacts. We have analyzed these effects as a function of material composition (Si excess fraction) and thickness, and also evaluated how the geometry of the detection setup affects the measurements. To correct the experimental photoluminescence spectra and extract the true spectral shape of the emission from Si nanocrystals, we have developed an algorithm based on a modulation function, which depends on both the multilayer sequence and the experimental configuration. This procedure can be easily extended to other heterogeneous systems.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.46.-w Structure of nanoscale materials
82.80.-d Chemical analysis and related physical methods of analysis
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close