APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

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

11 Jan 1999

Volume 74, Issue 2, pp. 161-325

Return to All Sections
back to top
RSS Feeds

Raman studies on phonon modes in cubic AlGaN alloy

H. Harima, T. Inoue, S. Nakashima, H. Okumura, Y. Ishida, S. Yoshida, T. Koizumi, H. Grille, and F. Bechstedt

Appl. Phys. Lett. 74, 191 (1999); http://dx.doi.org/10.1063/1.123289 (3 pages) | Cited 39 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Cubic AlxGa1−xN alloy layers have been successfully grown for x = 0−1 by gas-source molecular beam epitaxy on cubic-SiC/Si substrates, and the compositional dependence of the transverse-optic (TO) and longitudinal-optic (LO) phonon modes has been studied by Raman scattering. The LO-mode frequency of mixed crystals shows a systematic variation from the pure cubic AlN phase to the cubic GaN phase (one-mode type). On the contrary, there are two branches for the TO mode varying slowly in frequency with the composition (two-mode type). This behavior is explained within a random-element-isodisplacement model including the effect of polarization field. Our result indicates a strong polarization field acting on the cation-nitrogen bonds. © 1999 American Institute of Physics.
Show PACS
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors

Nanotube self-organization: Formation by step-flow growth

Oleg A. Louchev and Yoichiro Sato

Appl. Phys. Lett. 74, 194 (1999); http://dx.doi.org/10.1063/1.123290 (3 pages) | Cited 24 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The growth kinetics of carbon nanotubes is considered within the framework of a step-flow kinetics model proposed in 1951 by Burton, Cabrera, and Frank [W. K. Burton, N. Cabrera, and F. C. Frank, Philos. Trans. R. Soc. London, Ser. A 243, 299 (1951)] as a general mechanism for defectless crystal growth. The model reveals that the nucleation of the next layer and its consecutive growth can inhibit the growth of the underlying layers leading to the formation of observed nanotubular “bamboo” structures. © 1999 American Institute of Physics.
Show PACS
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
64.60.Q- Nucleation
81.07.-b Nanoscale materials and structures: fabrication and characterization

Well-aligned carbon nitride nanotubes synthesized in anodic alumina by electron cyclotron resonance chemical vapor deposition

S. L. Sung, S. H. Tsai, C. H. Tseng, F. K. Chiang, X. W. Liu, and H. C. Shih

Appl. Phys. Lett. 74, 197 (1999); http://dx.doi.org/10.1063/1.123291 (3 pages) | Cited 70 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Vertically aligned carbon nitride nanotubes with a uniform diameter of about 250 nm have been synthesized on a porous alumina membrane template (50–80 μm thick) in a microwave excited plasma of C2H2 and N2 using an electron cyclotron resonance chemical vapor deposition system. A negative dc bias voltage was applied to the substrate holder of graphite to promote the flow of ionic fluxes through the nanochannels of the alumina template. This allowed the physical, and subsequent chemical, absorption of species on the walls of the nanochannels that resulted in the formation of the carbon nitride nanotubes. The hollow structure and vertically aligned properties of the nanotubes have been clearly verified by field-emission scanning electron microscope images. The absorption band between 1250 and 1750 cm−1 in the Fourier transform infrared spectroscopy spectrum proves that nitrogen atoms have been incorporated into an amorphous network of carbon. © 1999 American Institute of Physics.
Show PACS
81.05.ub Fullerenes and related materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
78.30.Na Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Tr Fullerenes and related materials
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Hydrogen uptake in alumina thin films synthesized from an aluminum plasma stream in an oxygen ambient

Jochen M. Schneider, André Anders, Björgvin Hjörvarsson, Ivan Petrov, Karol Macák, Ulf Helmersson, and Jan-Eric Sundgren

Appl. Phys. Lett. 74, 200 (1999); http://dx.doi.org/10.1063/1.123292 (3 pages) | Cited 38 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We describe the hydrogen uptake during the synthesis of alumina films from H2O present in the high vacuum gas background. The hydrogen concentration in the films was determined by the 1H(15N,αγ)12C nuclear resonance reaction. Furthermore, we show the presence of hydrogen ions in the plasma stream by time-of-flight mass spectrometry. The hydrogen content increased in both the film and the plasma stream, as the oxygen partial pressure was increased. On the basis of these measurements and thermodynamic considerations, we suggest that an aluminum oxide hydroxide compound is formed, both on the cathode surface as well as in the film. The large scatter in the data reported in the literature for refractive index and chemical stability of alumina thin films can be explained on the basis of the suggested aluminum oxide hydroxide formation. © 1999 American Institute of Physics.
Show PACS
68.55.Nq Composition and phase identification
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Bonding configurations of nitrogen absorption peak at 960 cm−1 in silicon oxynitride films

Haruhiko Ono, Taeko Ikarashi, Yoshinao Miura, Eiji Hasegawa, Koichi Ando, and Tomohisa Kitano

Appl. Phys. Lett. 74, 203 (1999); http://dx.doi.org/10.1063/1.123293 (3 pages) | Cited 20 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigated bonding configurations of nitrogen atoms in silicon oxynitride films, resulting in a 960 cm−1 absorption peak, which is a higher frequency than that for Si3N4 (840 cm−1). The 960 cm−1 peak was observed in the films for which an N 1s x-ray photoemission peak was observed with a binding energy of about 398.6 eV, which has been reported as a binding energy associated with the �Si–N–Si� structure. However, the 960 cm−1 peak was absent in the films for which the N 1s peak was observed at about 397.8 eV, being close to the binding energy associated with the Si3�N structure. We conclude that the absorption peak at 960 cm−1 arises from the �Si–N–Si� structure of doubly bonded N atoms with two Si atoms, not affected by any oxygen atoms. © 1999 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
61.50.Lt Crystal binding; cohesive energy
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators

Electric-field-induced insulator–metal transitions in thin films of charge-ordered rare-earth manganates

V. Ponnambalam, Sachin Parashar, A. R. Raju, and C. N. R. Rao

Appl. Phys. Lett. 74, 206 (1999); http://dx.doi.org/10.1063/1.123294 (3 pages) | Cited 50 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Thin films of charge-ordered Nd0.5Ca0.5MnO3, Y0.5Ca0.5MnO3, and Nd0.5Sr0.5MnO3 have been prepared on Si(100) and LaAlO3(100) substrates by the nebulized spray pyrolysis of organometallic precursors. Small electric fields induce insulator–metal transitions in the films with the resistivity decreasing with increasing current. The current–voltage characteristics are non-ohmic and show some hysteresis. The current-induced negative differential resistance found in these manganate films could have potential technological applications. © 1999 American Institute of Physics.
Show PACS
73.61.Ng Insulators
75.47.Gk Colossal magnetoresistance
72.60.+g Mixed conductivity and conductivity transitions
73.50.Fq High-field and nonlinear effects
75.70.Ak Magnetic properties of monolayers and thin films
71.30.+h Metal-insulator transitions and other electronic transitions
71.45.-d Collective effects

Two species model for deposition and erosion of carbon-nitrogen films

F. D. A. Aarão Reis and D. F. Franceschini

Appl. Phys. Lett. 74, 209 (1999); http://dx.doi.org/10.1063/1.123295 (3 pages) | Cited 9 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We propose a model of random deposition and erosion for carbon–nitrogen film growth. Particles C and N represent carbon and nitrogen atoms and are released with probabilities p and 1−p, respectively. Particle C aggregates upon contact with the surface. Particle N annihilates with a top C (N) with a probability of q (1). The line p = q/2 separates the regimes of growth and erosion. As p decreases for fixed q the deposition rate decreases, while the bulk concentration of N and the surface roughness increase. It describes qualitatively the growth of plasma deposited carbon–nitrogen films, and is in good quantitative agreement with results in acetylene–nitrogen atmospheres. © 1999 American Institute of Physics.
Show PACS
81.15.Aa Theory and models of film growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.60.Bs Mechanical and acoustical properties
62.20.Qp Friction, tribology, and hardness

Femtosecond pump-probe investigation on relaxation of photoexcitations and spectral narrowing of photoluminescence for poly(para-phenylenevinylene)

Sae Chae Jeoung, Yong Hee Kim, Dongho Kim, Ja-Young Han, Min Sik Jang, Jung-Ik Lee, Hong-Ku Shim, Cheon Min Kim, and Choon Sup Yoon

Appl. Phys. Lett. 74, 212 (1999); http://dx.doi.org/10.1063/1.123296 (3 pages) | Cited 3 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photoinduced absorption spectra and their temporal profiles of poly(para-phenylenevinylene) thin film exhibit a strong correlation with an appearance of spectrally narrowed emission bands. The dependence of transient absorption signals on excitation and probe power denotes much lower saturation intensity in photoinduced absorption than that in stimulated emission arising from the identical photoexcitations, singlet excitons. We interpreted the peculiar emission bands in terms of superradiance or superfluorescence with a time constant of around 1 ps rather than amplification of spontaneous emission from uncorrelated emitters. © 1999 American Institute of Physics.
Show PACS
78.66.Qn Polymers; organic compounds
78.47.-p Spectroscopy of solid state dynamics
78.55.Kz Solid organic materials

Photomelting of selenium at low temperature

Vladimir V. Poborchii, Alexander V. Kolobov, and Kazunobu Tanaka

Appl. Phys. Lett. 74, 215 (1999); http://dx.doi.org/10.1063/1.123297 (3 pages) | Cited 35 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on a photoinduced phenomenon in solids, namely, photomelting at low temperature. We have found that both trigonal and amorphous selenium can be molten by illumination with light at a temperature of ∼ 77 K. This phenomenon is pure optical (athermal) and it is associated with light-induced breaking of the interchain (intermolecular) bonds in selenium. The photomelting is important for basic science (as an example of photoinduced phase transition in condensed matter and as a key photoinduced phenomenon in selenium and related materials) and for applications (as a tool for fine manipulation with shape of solids by light at low temperatures). © 1999 American Institute of Physics.
Show PACS
61.50.Lt Crystal binding; cohesive energy
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
79.20.Ds Laser-beam impact phenomena

Annealing effects and Te mixing in CdTe/CdS heterojunctions

Y. L. Soo, S. Huang, Y. H. Kao, and A. D. Compaan

Appl. Phys. Lett. 74, 218 (1999); http://dx.doi.org/10.1063/1.123298 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Angular dependence of x-ray fluorescence techniques have been employed to investigate the effects of thermal annealing at various temperatures ranging from 340 to 387 °C on a series of CdTe/CdS heterojunctions. Changes in depth profiles of Te and Cd atoms in the CdS layer as a result of heat treatment has been observed. A simple model is proposed for comparison of the ratio of Te Kα to Cd Kα fluorescence yield at different annealing temperatures. Our results suggest that the concentration of migrated Te atoms in the CdS layer increases with the annealing temperature, and the Te/Cd ratio in the CdS layer could even become greater than that in CdTe with annealing temperatures higher than 370 °C. © 1999 American Institute of Physics.
Show PACS
68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Cc Kinetics of defect formation and annealing
78.66.Hf II-VI semiconductors

Silicon vacancy in SiC: A high-spin state defect

L. Torpo, R. M. Nieminen, K. E. Laasonen, and S. Pöykkö

Appl. Phys. Lett. 74, 221 (1999); http://dx.doi.org/10.1063/1.123299 (3 pages) | Cited 31 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report results from spin-polarized ab initio local spin-density calculations for the silicon vacancy (VSi) in 3C– and 2H–SiC in all its possible charge states. The calculated electronic structure for SiC reveals the presence of a stable spin-aligned electron-state t2 near the midgap. The neutral and doubly negative charge states of VSi in 3C–SiC are stabilized in a high-spin configuration with S = 1 giving rise to a ground state, which is a many-electron orbital singlet 3T1. For the singly negative VSi, we find a high-spin ground-state 4A2 with S = 3/2. In the high-spin configuration, VSi preserves the Td symmetry. These results indicate that in neutral, singly, and doubly negative charge states a strong exchange coupling, which prefers parallel electron spins, overcomes the Jahn–Teller energy. In other charge states, the ground state of VSi has a low-spin configuration. © 1999 American Institute of Physics.
Show PACS
71.55.Ht Other nonmetals
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
61.72.J- Point defects and defect clusters
71.70.Gm Exchange interactions

Mechanism of enhanced formation of C54–TiSi2 in high-temperature deposited Ti thin films on preamorphized (001)Si

S. M. Chang, H. Y. Huang, H. Y. Yang, and L. J. Chen

Appl. Phys. Lett. 74, 224 (1999); http://dx.doi.org/10.1063/1.123300 (3 pages) | Cited 17 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Enhanced formation of C54-TiSi2 in high-temperature deposited Ti thin films on preamorphized (001)Si has been investigated by high-resolution transmission electron microscopy in conjunction with autocorrelation function analysis. The increase in the thickness of the amorphous TiSix layer is due to the preamorphization implantation for the most part. The dominant effect of high-temperature sputtering is to increase the density of crystallites in the amorphous TiSix layer. The enhanced formation of C54–TiSi2 in high-temperature deposited samples is attributed to the more extensive presence of silicide crystallites, which serve as nucleation sites, in the amorphous TiSix layer than that in samples deposited at room temperature. © 1999 American Institute of Physics.
Show PACS
68.35.Fx Diffusion; interface formation
85.40.Ls Metallization, contacts, interconnects; device isolation
64.70.K- Solid-solid transitions
68.55.-a Thin film structure and morphology
61.72.uf Ge and Si
81.15.Cd Deposition by sputtering
61.72.Cc Kinetics of defect formation and annealing
73.61.At Metal and metallic alloys

Confirmation of proton beam bending in graded Si1−xGex/Si layers using ion channeling

D. G. de Kerckhove, M. B. H. Breese, P. J. M. Smulders, and D. N. Jamieson

Appl. Phys. Lett. 74, 227 (1999); http://dx.doi.org/10.1063/1.123034 (3 pages) | Cited 2 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A graded composition Si1−xGex/Si [001] layer, which has recently been proposed as a method for bending and extracting protons from high-energy particle accelerators, has been studied by angle-resolved ion channeling analysis using focused MeV proton and He+ beams. Backscattering spectrometry confirms that the composition is linearly graded and a maximum Ge concentration of 0.16 was measured at the epilayer surface. Off-normal planes {111} are curved with respect to the substrate by a total angle of 0.332° and efficient bending of channeled particles along the curved planes and into the substrate is confirmed. © 1999 American Institute of Physics.
Show PACS
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
29.27.Ac Beam injection and extraction
29.27.Eg Beam handling; beam transport

Conducting barriers for vertical integration of ferroelectric capacitors on Si

S. Aggarwal, A. M. Dhote, H. Li, S. Ankem, and R. Ramesh

Appl. Phys. Lett. 74, 230 (1999); http://dx.doi.org/10.1063/1.123301 (3 pages) | Cited 11 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
One of the issues impeding the commercialization of nonvolatile ferroelectric memories is the identification and development of a conducting diffusion barrier for the vertical integration of ferroelectric capacitors on Si-based transistors. We report results on the use of Ti–Al alloys as such a diffusion barrier. Our results indicate that it maintains its structural integrity and electrical conductivity after the deposition of a lead-based ferroelectric stack at 650 °C. The electrical properties of the capacitors were measured through the barrier layer by making direct contact to the diffusion barrier. The properties of the capacitors measured by direct contact to the Ti–Al alloy show clearly the absence of an insulating interfacial layer. Transmission electron microscopy and Rutherford backscattering studies confirm that there is no oxidation of the conducting barrier and no reaction between it and the electrode. © 1999 American Institute of Physics.
Show PACS
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
85.40.Sz Deposition technology
73.61.At Metal and metallic alloys
81.15.Fg Pulsed laser ablation deposition
68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology

Nanoscale reconstruction of surface crystallography from three-dimensional polarization distribution in ferroelectric barium–titanate ceramics

L. M. Eng, H.-J. Güntherodt, G. A. Schneider, U. Köpke, and J. Muñoz Saldaña

Appl. Phys. Lett. 74, 233 (1999); http://dx.doi.org/10.1063/1.123266 (3 pages) | Cited 93 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The three-dimensional orientation of polarization vectors at the surface of ferroelectric barium–titanate (BaTiO3) ceramics is evaluated using voltage-modulated scanning force microscopy (SFM). By applying an ac voltage to the conductive SFM tip, we measure the relative amount of the three orthogonal components Px, Py, and Pz, of the polarization vector at any surface point. The measured polarization orientation together with the actual domain-wall orientation allows a precise reconstruction of the crystallographic orientation of the investigated grains down to a 40 nm resolution. Excellent agreement is obtained when comparing this orientation with the crystallographic reconstruction revealed by etch patterns from the sample surface topography. We show that the surface topography manifests a domain structure, which was present in the past, while the actual ferroelectric domain configuration is revealed by the modulation technique. © 1999 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.35.B- Structure of clean surfaces (and surface reconstruction)
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
81.65.Cf Surface cleaning, etching, patterning
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Multiphoton-excited luminescence from diamond nanoparticles and an evolution to emission accompanying the laser vaporization process

Yu. D. Glinka, K.-W. Lin, and S. H. Lin

Appl. Phys. Lett. 74, 236 (1999); http://dx.doi.org/10.1063/1.122998 (3 pages) | Cited 1 time

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The photoluminescence (PL) from 100 nm diamond particles induced by infrared (IR) pulsed excitation [λexc = 1064 nm (1.16 eV), τ=10 ns] was observed. The laser light intensity dependence of the PL yield shows that this is the five-photon absorption process (the total energy of excitation 5.8 eV). The PL results from structure defects, impurities, and the graphite-like phase excited by a relaxation of the multiphoton (MP)—produced electron–hole pairs (the band gap of diamond Eg = 5.5 eV). By using the ultraviolet one-photon excitation [λexc = 354.7 nm (3.48 eV), τ=10 ns], the same PL bands were observed in support of the correctness of interpretation. The typical Swan bands of electronically excited C2 species dominate the spectra at the IR light intensity above the threshold for vaporization. It was concluded that the MP-excited PL precedes the emission accompanying the laser vaporization process. © 1999 American Institute of Physics.
Show PACS
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.66.Tr Fullerenes and related materials
78.66.Vs Fine-particle systems
81.05.ub Fullerenes and related materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
64.70.Hz Solid-vapor transitions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.05.Cy Elemental semiconductors

Nonlinear optical response of Ge nanocrystals in a silica matrix

A. Dowd, R. G. Elliman, M. Samoc, and B. Luther-Davies

Appl. Phys. Lett. 74, 239 (1999); http://dx.doi.org/10.1063/1.123267 (3 pages) | Cited 24 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Time-resolved degenerate-four-wave-mixing measurements were used to study the nonlinear optical response (intensity-dependent refractive index) of Ge nanocrystallites embedded in a silica matrix. Nanocrystals were fabricated by ion-implanting silica with 1.0 MeV Ge ions to fluences in the range from 0.6 to 3×1017 Ge cm−2, followed by annealing at 1100 °C for 60 min. For the highest fluence, this resulted in nanocrystals with a log-normal size distribution, having a geometric mean diameter of 3.0 nm and a dimensionless geometric standard deviation of 0.25. The intensity-dependent refractive index ∣n2∣ was measured at a wavelength of 800 nm and found to increase linearly with increasing Ge fluence. For the highest fluence, ∣n2∣ was determined to be in the range 2.7–6.9×10−13 cm−2 W−1, depending on the duration of the excitation pulse; values were consistently smaller for shorter pulse lengths. Relaxation of the nonlinear response was found to have two characteristic time constants, one <100 fs and the other ∼1 ps. © 1999 American Institute of Physics.
Show PACS
78.66.Db Elemental semiconductors and insulators
61.46.-w Structure of nanoscale materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.47.-p Spectroscopy of solid state dynamics
61.72.Cc Kinetics of defect formation and annealing

Electrochromic mechanism in a-WO3−y thin films

Se-Hee Lee, Hyeonsik M. Cheong, Ji-Guang Zhang, Angelo Mascarenhas, David K. Benson, and Satyen K. Deb

Appl. Phys. Lett. 74, 242 (1999); http://dx.doi.org/10.1063/1.123268 (3 pages) | Cited 59 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electrochromic mechanism in amorphous tungsten oxide films is studied using Raman scattering measurements. The Raman spectra of as-deposited films show two strong peaks at 770 and 950 cm−1 due to vibrations of the W6+–O and W6+☒O bonds, respectively, and a weaker peak at 220 cm−1 that we attribute to the W4+–O bonds. When lithium or hydrogen ions and electrons are inserted, extra Raman peaks due to W5+–O and W5+☒O bonds appear at 330 and 450 cm−1, respectively. Comparison of the Raman spectra of sputtered isotopic a-W16O3−y and a-W18O3−y films confirms these assignments. We conclude that the as-deposited films contain mainly the W4+ and W6+ states, and the W5+ states are generated as a result of reduction of the W6+ states when lithium or hydrogen ions and electrons are inserted. We propose that the optical absorption in the colored films is caused by transitions between the W6+ and W5+, and W5+ and W4+ states. © 1999 American Institute of Physics.
Show PACS
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Nk Insulators
78.20.Jq Electro-optical effects
61.43.Er Other amorphous solids

Room-temperature deep-ultraviolet-stimulated emission from AlxGa1−xN thin films grown on sapphire

T. J. Schmidt, Yong-Hoon Cho, J. J. Song, and Wei Yang

Appl. Phys. Lett. 74, 245 (1999); http://dx.doi.org/10.1063/1.123269 (3 pages) | Cited 11 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Room-temperature deep-ultraviolet-stimulated emission (SE) has been observed from optically pumped metalorganic chemical vapor deposition grown AlxGa1−xN thin films. SE has been observed for Al concentrations as high as x = 0.26, with a resultant SE wavelength as low as 328 nm at room temperature. The results obtained for the AlxGa1−xN layers are compared with InxGa1−xN layers of comparable alloy concentration and GaN reference layers. The incorporation of Al into GaN is shown to result in AlxGa1−xN layers with similar high excitation-density emission behavior as GaN, in contrast to InxGa1−xN layers, which exhibit markedly different SE behavior. The observation of room-temperature SE from AlxGa1−xN layers of significant Al concentration illustrates the suitability of AlxGa1−xN based structures, not only for use in deep-ultraviolet detectors, but also as a potential source of deep-ultraviolet laser radiation. © 1999 American Institute of Physics.
Show PACS
78.45.+h Stimulated emission
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close