Effect of Stress on the Carrier Contribution to Elastic Constants in Thin Films of Small Gap Compounds

1993 ◽  
Vol 308 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
Sambhu Nath Biswas
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Experimental Method ◽  
Elastic Constants ◽  
Electron Concentration ◽  
Ultrathin Films ◽  
Theoretical Formulation ◽  
Lattice Matched

ABSTRACTIn this paper we have investigated the carrier contribution to elastic constants in very thin films of stressed small gap compounds within the domain of theory. It is found, taking stressed ultrathin films Hg1-xCdxTe and In1-xGaxAsyP1-y lattice matched to InP as examples, that the elastic constants increase with increasing electron concentration and decreasing film thickness respectively in oscillatory manners. Besides the stress enhances the numerical values of such contribution to the elastic constants. In addition, the theoretical formulation is in agreement with the suggested experimental method of determining such constants in materials having arbitary dispersion laws.

On The Electronic Contribution to Elastic Constants of Ultrathin Films of P-Type Si

1991 ◽  
Vol 226 ◽  
Author(s):  
Kamaxhya P Ghatak ◽  
Badal De
Keyword(s):  
Film Thickness ◽  
Experimental Method ◽  
Elastic Constants ◽  
Ultrathin Films ◽  
Hole Concentration ◽  
Electronic Contribution ◽  
Third Order ◽  
Theoretical Formulation ◽  
Third Order Elastic Constants ◽  
P Type

AbstractIn this paper we have formulated the electronic contribution to the elastic constants in ultrathin films of p-Si by considering the influences of heavy, light and split-off holes respectively. We have suggested an experimental method of determining the same in degenerate materials having arbitrary dispersion laws. The elastic constants increase with increasing hole concentration in an oscillatory way and decrease with increasing film thickness. The theoretical formulation is in agreement with the suggested experimental method of determining second and third order elastic constants.

The Electronic Contribution to The Elastic Constants of Strained III-V Materials Under High Magnetic Fields

1995 ◽  
Vol 379 ◽  
Author(s):  
Kamakhya P Ghatak ◽  
B. Nag ◽  
G. Mazumder
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Experimental Method ◽  
Elastic Constants ◽  
Quantitative Agreement ◽  
High Magnetic Fields ◽  
Electronic Contribution ◽  
Theoretical Formulation ◽  
Wide Gap ◽  
Lattice Matched

ABSTRACTIn this paper an attempt is made to study the electronic contribution to the elastic constants of strained III-V materials under high magnetic fields on the basis of k.p theory. It is found taking strained Hgi - x CdxTe and Ini - xGaxAsyPi-y lattice matched InP as examples that they increase with increasing doping and oscillate with inverse magnetic field respectively. The strain enhances the numerical values of the elastic constants. The theoretical formulation is in quantitative agreement with the suggested experimental method of determining the above contributions for degenerate materials having arbitrary dispersion laws. In addition, the well-known results for strain free wide gap materials in the absence of magnetic field have been obtained from our generalized analysis under certain limiting conditions.

The Influence of Quantizing Magnetic Field on The Magnetic Susceptibilities in Ultra Thin Films of Dilute Magnetic Materials

1993 ◽  
Vol 313 ◽  
Author(s):  
Kamakhya P Ghatak ◽  
S. N. Biswas
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Thin Films ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Magnetic Materials ◽  
Ultrathin Films ◽  
Surface Concentration ◽  
Magnetic Susceptibilities ◽  
Quantizing Magnetic Field

ABSTRACTIn this paper we have studied the dia and paramagnetic susceptibilities of the holes in ultrathin films of dilute magnetic materials in the presence of a quantizing magnetic field and compared the same with that of the bulk specimens under magnetic quantization for the purpose of relative comparison. It is found, taking Hg1−xMnxTe and Cd1−xMnxSe as examples, that both the susceptibilities increase with decreasing film thickness and increasing surface concentration in oscillatory Manners. The numerical values of the susceptibilities in ultrathin films of dilute magnetic materials are greater than that of the bulk and the theoretical analysis is in agreement with the experimental data as reported elsewhere.

On thon the Photoemission from Quantum Confined Strained III–V Systems

1995 ◽  
Vol 379 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
B. Nag ◽  
G. Mazumder
Keyword(s):  
Quantum Dots ◽  
Film Thickness ◽  
Quantum Wells ◽  
Electron Concentration ◽  
Quantum Confinement ◽  
Dispersion Law ◽  
Quantum Confined ◽  
Electron Dispersion ◽  
Lattice Matched ◽  
Theoretical Results

ABSTRACTIn this paper we have studied the photoemission from quantum wells (QW), quantum wells wires (QWWs) and quantum dots (QDs) of quantum confined strained III–V compounds on the basis of a newly formulated electron dispersion law. It is found taking such quantum confined Hg1–xCdxTe and In1–xGaxAsyP1–y lattice matched InP as examples that the photoemission increases with increasing energy of the incident photons in a ladder like manner and also exhibits oscillatory dependences with changing electron concentration and film thickness respectively for all types quantum confinement. The photoemitted current is greatest in strained QDs and least in unstrained QWs. In addition the theoretical results are in agreement with the experimental datas as given elsewhere.

On the Thermoelectric Power in Ultrathin Films of A3IIB2V Semiconductors Under Magnetic Quantization

1991 ◽  
Vol 234 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
Badal De
Keyword(s):  
Energy Spectrum ◽  
Film Thickness ◽  
Thermoelectric Power ◽  
Electron Concentration ◽  
Ultrathin Films ◽  
Surface Electron ◽  
Magnetic Quantization ◽  
Theoretical Results

ABSTRACTAn attempt is made to study the thermoelectric power in ultrathin films of semiconductors under magnetic quantization by including all types of aniso tropies in the energy spectrum within the domain of theory, and taking n-Cd3As2 as an example. It is found that, the magne to-thermopower decreases with increasing surface electron concentration and also changes in an oscillatory manner with film thickness respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.

Advanced Resonant-Ultrasound Spectroscopy for Studying Anisotropic Elastic Constants of Thin Films

2005 ◽  
Vol 875 ◽  
Author(s):  
Hirotsugu Ogi ◽  
Nobutomo Nakamura ◽  
Hiroshi Tanei ◽  
Masahiko Hirao
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Film Thickness ◽  
Elastic Constants ◽  
Elastic Anisotropy ◽  
Thickness Direction ◽  
Resonant Ultrasound Spectroscopy ◽  
Out Of Plane ◽  
Resonant Ultrasound ◽  
Anisotropic Elastic

AbstractThis paper presents two advanced acoustic methods for the determination of anisotropic elastic constants of deposited thin films. They are resonant-ultrasound spectroscopy with laser-Doppler interferometry (RUS/Laser method) and picosecond-laser ultrasound method. Deposited thin films usually exhibit elastic anisotropy between the film-growth direction and an in-plane direction, and they show five independent elastic constants denoted by C11,C33,C44,C66 and C13 when the x3 axis is set along the film-thickness direction. The former method determines four moduli except C44, the out-of-plane shear modulus, through free-vibration resonance frequencies of the film/substrate specimen. This method is applicable to thin films thicker than about 200 nm. The latter determines C33, the out-of-plane modulus, accurately bymeasuring the round-trip time of the longitudinal wave traveling along the film-thickness direction. This method is applicable to thin films thicker than about 20 nm. Thus, combination of these two methods allows us to discuss the elastic anisotropy of thin films. The results for Co/Pt superlattice thin film and copper thin film are presented.

Giant Anisotropy of Conductivity in Hydrogenated Nanocrystalline Silicon Thin Films

1998 ◽  
Vol 536 ◽  
Author(s):  
A. B. Pevtsov ◽  
N. A. Feoktistov ◽  
V. G. Golubev
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Percolation Theory ◽  
Nanocrystalline Silicon ◽  
Spatial Light Modulators ◽  
Light Emitting ◽  
Light Modulators ◽  
Silicon Thin Films ◽  
Longitudinal Conductivity ◽  
Transverse Conductivity

AbstractThin (<1000 Å) hydrogenated nanocrystalline silicon films are widely used in solar cells, light emitting diodes, and spatial light modulators. In this work the conductivity of doped and undoped amorphous-nanocrystalline silicon thin films is studied as a function of film thickness: a giant anisotropy of conductivity is established. The longitudinal conductivity decreases dramatically (by a factor of 109 − 1010) as the layer thickness is reduced from 1500 Å to 200 Å, while the transverse conductivity remains close to that of a doped a- Si:H. The data obtained are interpreted in terms of the percolation theory.

scholarly journals Optical Constant and Conformality Analysis of SiO2 Thin Films Deposited on Linear Array Microstructure Substrate by PECVD

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 510
Author(s):  
Yongqiang Pan ◽  
Huan Liu ◽  
Zhuoman Wang ◽  
Jinmei Jia ◽  
Jijie Zhao
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Deposition Rate ◽  
Optical Constant ◽  
Photoelectron Spectroscopy ◽  
Linear Array ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
X Ray ◽  
Sio2 Thin Film

SiO2 thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH4 and N2O as precursor gases. The stoichiometry of SiO2 thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO2 thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO2 thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO2 thin films are studied. The conformality of SiO2 thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO2 thin film from 20.84 to 41.92 nm/min. The conformality of SiO2 thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO2 thin films.

scholarly journals Emergence and Evolution of Crystallization in TiO2 Thin Films: A Structural and Morphological Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1409
Author(s):  
Ofelia Durante ◽  
Cinzia Di Giorgio ◽  
Veronica Granata ◽  
Joshua Neilson ◽  
Rosalba Fittipaldi ◽  
...  
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Transition Metal Oxides ◽  
Annealing Temperature ◽  
Morphological Properties ◽  
Degree Of Crystallinity ◽  
Tio2 Thin Films ◽  
Force Microscopy ◽  
Heat Treated ◽  
Complementary Techniques

Among all transition metal oxides, titanium dioxide (TiO2) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO2 thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250–1000 °C, and the TiO2 thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO2 thickness and annealing temperature, both ultimately affecting the degree of crystallinity.

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