Laser Stimulated Deposition of GaAs, GaAsP and GaAsP-GaAs Superlattices

1986 ◽  
Vol 75 ◽  
Author(s):  
N. H. Karam ◽  
S. M. Bedair ◽  
N. A. El-Masry ◽  
D. Griffis
Keyword(s):  
Laser Beam ◽  
Growth Conditions ◽  
Direct Writing ◽  
Gaas Substrates ◽  
Laser Beam Irradiation ◽  
Single Crystal Films ◽  
Crystal Films ◽  
Potential Applications ◽  
Ion Laser ◽  
Deposited Films

AbstractAn Ar+ ion laser has been used for direct writing of GaAs and GaAsP single crystal films on thermally biased GaAs substrates. Multiple scanning of the laser beam at speeds in the range 100–200 μm/s at carefully selected growth conditions resulted in single crystalline selectively deposited films. Photoluminescence indicates that these deposited films have optical properties that are comparable with the conventionally (MOCVD) grown material. Laser beam irradiation has been used to form a superlattice (SL) structure which has been demonstrated in the GaAsP-GaAs system. When a GaAs substrate is exposed to fluxes of AsH3, PH3 and TMG at 500°C, only GaAs will be deposited because of the insufficient cracking of PH3. However, localized laser heating results in GaAsP deposition. A GaAsP-GaAs superlattice with a period of about 400 Å has been synthesized. This laser induced technique can thus have potential applications in the generation of abrupt interfaces without the use of shutters as in MBE or gas switching as in MOCVD.

Laser Enhanced Selective Epitaxy of ιii-V Compounds

1987 ◽  
Vol 101 ◽  
Author(s):  
N.H. Karam ◽  
H. Liu ◽  
I. Yoshida ◽  
T. Katsuyama ◽  
S.M. Bedair ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Atomic Layer ◽  
Growth Conditions ◽  
Direct Writing ◽  
Growth Technique ◽  
X Ray ◽  
Selective Epitaxial Growth ◽  
Gaas Substrates ◽  
Ion Laser

ABSTRACTSelective epitaxial growth of III-V compounds based on GaAs has been achieved using Ar+ ion laser assisted chemical vapor deposition (LCVD) on GaAs substrates. The growth rate, at carefully selected growth conditions, can be controlled to a few Å/s at bias temperatures as low as 250°C by conventional LCVD multi-scan technique. Typical Gaussian thickness profiles are achieved by this growth technique. On the other hand, flat top thickness profiles are achieved with direct writing of GaAs mono-layers by laser assisted atomic layer epitaxy (LALE). X-ray topography is demonstrated as a powerful tool for characterizing the grown films and photoluminescence shows that the quality of the grown films are comparable with those grown by conventional MOCVD or ALE.

Precipitation in Al + 4% Cu Epitaxial Films

1968 ◽  
Vol 26 ◽  
pp. 384-385
Author(s):  
S. Herd ◽  
S. M. Mader
Keyword(s):  
Solid Solution ◽  
Bulk Material ◽  
Epitaxial Films ◽  
Detectable Change ◽  
Cu Films ◽  
Solution Treated ◽  
Single Crystal Films ◽  
Crystal Films ◽  
Diffraction Patterns ◽  
Deposited Films

Single crystal films in (001) orientation, about 1500 Å thick, were produced by R-F sputtering of Al + 4 wt % Cu onto cleaved KCl at 150°C substrate temperature. The as-deposited films contained numerous θ-CuAl2 particles (C16 structure) about 0.1μ in size. They were transferred onto Mo screens, solution treated and rapidly cooled (within about ½ min) so as to retain a homogeneous solid solution. Subsequently, the films were aged in vacuum at various temperatures in order to induce precipitation and to compare structures and morphologies of precipitate particles in Al-Cu films with those found in age hardened bulk material.Aging for 3 weeks at 60°C or 48 hrs at 100°C did not produce any detectable change in high resolution micrographs or diffraction patterns. In this range Guinier-Preston zones (GP) form in quenched bulk material. The absence of GP in the present experiments in this aging range is perhaps due to the cooling rate employed, which might be more equivalent to an aged and reverted bulk material than to a quenched one.

Epitaxial Ge/GaAs Heterostructures by Scanned CW Laser Annealing of a-GE Layers on GaAS

1981 ◽  
Vol 4 ◽  
Author(s):  
J.E. Greene ◽  
K.C. Cadien ◽  
D. Lubben ◽  
G.A. Hawkins ◽  
G.R. Erikson ◽  
...  
Keyword(s):  
Single Crystal ◽  
Laser Power ◽  
Laser Annealing ◽  
Beam Diameter ◽  
Primary Interest ◽  
Explosive Crystallization ◽  
Gaas Substrates ◽  
Scan Rate ◽  
Single Crystal Films ◽  
Crystal Films

ABSTRACTEpitaxial regrowth of Ge/GaAs heterostructures by scanned laser annealing of amorphous Ge films on GaAs substrates has been studied as a function of laser power and scan rate. At least eight regimes representing different film regrowth characteristics were observed. Of these, two were of primary interest. At low powers (between~1.6 and 3.2 W for a beam diameter of~40 μm) and scan rates between 1 and 400 cm/sec, polycrystalline Ge with a (100) preferred orientation was formed by an “explosive” crystallization mechanism. At higher powers, and over a scan rate range of 25 to 400 cm/sec, single crystal metastable (GaAs)1−x Gexalloys were obtained by liquid phase regrowth. Typical film resistivities, ρ, were as follows: as-deposited ρ=180Ωcm; polycrystalline films, ρ=3 × 10−2 Ωcm; single crystal films,ρ=9×10−4Ωcm.

A new method for preparing tilt grain boundaries in thin vapor-deposited films

1987 ◽  
Vol 45 ◽  
pp. 280-281
Author(s):  
William Krakow ◽  
Victor Castaño
Keyword(s):  
Grain Boundaries ◽  
Boundary Migration ◽  
Ion Milling ◽  
The Past ◽  
Single Crystal Films ◽  
Crystal Films ◽  
Tilt Boundaries ◽  
Deposited Films ◽  
Twist Boundaries

In the past the electron microscope samples used to study tilt grain boundaries and interfaces were prepared from bulk samples grown from the melt which were then cut, polished and thinned by ion milling or chemical jet etching. This technique is also employed routinely in preparing crossectional semiconductor materials and metals. Another technique to prepare tilt boundaries in metals is to fuse two thin single crystal films each on substrates by heating and forming twist boundaries (e.g. Au (100)). Then, the boundary which forms at the composite film midplane, migrates to one of the two films surfaces having many island grains separated by tilt boundaries perpendicular to the foils’ surface. One of the present authors has carried this technique further by being able to perform this process directly in the microscope and observe the boundary migration when the total film thickness, in the case of Au, was ∼250Å. The technique is limited to this composite thickness because small holes develop in thinner films which thin rapidly become discontinuous when heated in-situ.

Circular flow formation triggered by Marangoni convection in nematic liquid crystal films with a free surface

Soft Matter ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 481-485 ◽  
Author(s):  
Hyunhee Choi ◽  
Hideo Takezoe
Keyword(s):  
Free Surface ◽  
Liquid Crystal ◽  
Laser Beam ◽  
Marangoni Convection ◽  
Beam Irradiation ◽  
Circular Flow ◽  
Liquid Crystal Films ◽  
Flow Formation ◽  
Laser Beam Irradiation ◽  
Crystal Films

We demonstrate circular flow formation at a surface in homeotropically oriented nematic liquid crystals with a free surface using focused laser beam irradiation.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

Bright-Field Images (Ctem) of Phase Objects at High Resolution

1976 ◽  
Vol 34 ◽  
pp. 490-491 ◽  
Author(s):  
Sumio Iijima
Keyword(s):  
High Resolution ◽  
Electron Beam Irradiation ◽  
Fine Particles ◽  
High Resolution Electron Microscopy ◽  
Good Test ◽  
Resolution Electron ◽  
Single Crystal Films ◽  
Crystal Films ◽  
By Products ◽  
Test Objects

We have developed a technique to prepare thin single crystal films of graphite for use as supporting films for high resolution electron microscopy. As we showed elsewhere (1), these films are completely noiseless and therefore can be used in the observation of phase objects by CTEM, such as single atoms or molecules as a means for overcoming the difficulties because of the background noise which appears with amorphous carbon supporting films, even though they are prepared so as to be less than 20Å thick. Since the graphite films are thinned by reaction with WO3 crystals under electron beam irradiation in the microscope, some small crystallites of WC or WC2 are inevitably left on the films as by-products. These particles are usually found to be over 10-20Å diameter but very fine particles are also formed on the film and these can serve as good test objects for studying the image formation of phase objects.

Novel organic, polymeric materials for electronics applications

2002 ◽  
Vol 722 ◽  
Author(s):  
Ram W. Sabnis ◽  
Mary J. Spencer ◽  
Douglas J. Guerrero
Keyword(s):  
Optical Density ◽  
Chemical Vapor ◽  
Polymeric Materials ◽  
Substantial Improvement ◽  
Polymeric Systems ◽  
Patterned Wafers ◽  
Visible Spectra ◽  
Potential Applications ◽  
Deep Ultraviolet ◽  
Deposited Films

AbstractNovel organic, polymeric materials and processes of depositing thin films on electronics substrates by chemical vapor deposition (CVD) have been developed and the lithographic behavior of photoresist coated over these CVD films at deep ultraviolet (DUV) wavelength has been evaluated. The specific monomers synthesized for DUV applications include [2.2](1,4)- naphthalenophane, [2.2](9,10)-anthracenophane and their derivatives which showed remarkable film uniformity on flat wafers and conformality over structured topography wafers, upon polymerization by CVD. The chemical, physical and optical properties of the deposited films have been characterized by measuring parameters such as thickness uniformity, solubility, conformality, adhesion to semiconductor substrates, ultraviolet-visible spectra, optical density, optical constants, defectivity, and resist compatibility. Scanning electron microscope (SEM) photos of cross-sectioned patterned wafers showed verticle profiles with no footing, standing waves or undercut. Resist profiles down to 0.10 νm dense lines and 0.09 νm isolated lines were achieved in initial tests. CVD coatings generated 96-100% conformal films, which is a substantial improvement over commercial spin-on polymeric systems. The light absorbing layers have high optical density at 248 nm and are therefore capable materials for DUV lithography applications. CVD is a potentially useful technology to extend lithography for sub-0.15 νm devices. These films have potential applications in microelectronics, optoelectronics and photonics.

scholarly journals Effects of ultraviolet laser beam irradiation on rabbit cornea and lens.

Sangyo Igaku ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 112-120 ◽  
Author(s):  
Sadafumi TAKISE ◽  
Shun'ichi HORIGUCHI ◽  
Ichiro KARAI ◽  
Shinya MATSUMURA ◽  
Makoto HARIMA ◽  
...  
Keyword(s):  
Laser Beam ◽  
Beam Irradiation ◽  
Rabbit Cornea ◽  
Ultraviolet Laser ◽  
Laser Beam Irradiation
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