Showing papers on "Pulsed laser deposition published in 1981"

Laser chemical vapor deposition: A technique for selective area deposition

Abstract: Laser chemical vapor deposition (LCVD) uses a focused laser beam to locally heat the substrate and drive the CVD deposition reacton. Several different deposition reactions and substrates have been examined as a function of intensity and irradiation time using a CO2 laser source: Ni on SiO2, TiO2 on SiO2, TiC on SiO2, and TiC on stainless steel. LCVD film thicknesses range from <100 A to ≳20 μm. Deposition rates of mm/min have been observed for LCVD Ni and 20 μm/min for LCVD TiO2. The diameter of the deposited films is dependent on irradiation conditions and can be as small as one tenth of the laser beam diameter. The LCVD films exhibit excellent physical properties such as adherence, conductivity, hardness, and smoothness.

Laser induced chemical vapor deposition of carbon

Abstract: Initial results on laser‐induced chemical vapor deposition using the visible radiation of an Ar+ laser are presented. Due to the smaller wavelength of Ar+ laser radiation in comparison to the infrared radiation of a CO2 laser used in earlier experiments, much finer patterns could be produced. The influence of laser irradiance on the deposition rate and widths of patterns was investigated.

Plasma enhanced deposition of semiconductors

Abstract: Semiconductor thin films are produced using plasma assisted chemical vapor deposition on alkali halide single crystal substrates. Deposition is formed at relatively low temperatures so that sublimation of the substrate is not a problem. The invention process permits at high rate deposition of high quality semiconductors.

A new low temperature III–V multilayer growth technique: Vacuum metalorganic chemical vapor deposition

Abstract: A new technique for multilayer growth by metalorganic chemical vapor deposition is described. The vacuum metalorganic chemical vapor deposition technique combines the low‐temperature growth capability of molecular beam epitaxy with the source handling system of chemical vapor deposition. The viability of the new technique is demonstrated by the growth of high‐mobility layers of GaAs, GaAs(1−x)P(x), and Ga(1−x)In(x)As at 570 °C. Room‐temperature mobilities of GaAs films as high as 4990 cm2/V s are obtained. Doping of both p‐type and n‐type films is demonstrated. GaAs shallow homojunction solar cells fabricated with this technique are described. Active‐area solar cell efficiencies as high as 19.6% are obtained with 6 ’’suns’’ AM2 concentrated light. This multilayer growth technique is particularly suited to the fabrication of multicolor solar cells.

Thermochemical action of laser radiation on thin metal films

Abstract: Laser-activated oxidation of thin metal films by the action of pulsed laser radiation is investigated theoretically and experimentally. A physical and mathematical model based on the Cabrera-Mott oxidation theory is developed. The basic relations, describing the process, are obtained numerically. Four different experimental methods have been used to examine qualitatively and quantitatively the laser-activated oxidation. The results obtained show that pulsed laser irradiation of thin metal films in the oxidizing environment may cause buildup of the thin oxide layer, which is very stable and may be used as a masking layer in the laser lithography. Comparison between experimental and theoretical results shows that the developed theoretical model describes the oxidation process well, and it may be used to find the optimum conditions for the thermochemical laser treatment of thin metal films.

Method for controlling the edge gradient of a layer of deposition material

Abstract: A method for controlling the slope of the edge gradient of a layer of vapor deposition material onto a substrate from an evaporation source of vapor deposition material comprising the steps of forming a flux of vapor deposition material having an effective source cross-sectional area and shape from an evaporation source of a vapor deposition material located at a known position, indexing a deposition mask having a plurality of apertures extending therethrough such that the mask is in a spaced relationship from the source defining a source-to-mask distance and positioned in the flux of vapor deposition material to permit the flux of vapor deposition to pass through the apertures, registering a substrate in a spaced relationship from the deposition mask defining a mask-to-substrate distance to permit the flux of the vapor deposition material passing through the apertures in the deposition mask to impinge onto the substrate forming a layer of vapor deposit material thereon, controlling at least one of the effective source cross-sectional area and shape of the flux of vapor deposition material, position of the evaporation source of a deposition material relative to the deposition mask, the magnitude of the substrate-to-mask distance and the magnitude of the mask-to-source distance to produce an edge onto the deposited layer of the vapor deposition material having the desired gradient is shown. A product produced by the process is also shown.

Plasma ion deposition process

Abstract: A plasma ion deposition process of large-grain, thin semiconductor films directly on low-cost amorphous substrates comprising ionizing a semiconductor-based gaseous compound in a chamber by an electron-supported large volume, low pressure, high temperature plasma. The semiconductor ions are extracted from the compound and are deposited on the substrate. Preferably, the deposition is effected first at a slow deposition rate, followed by a higher deposition rate. The deposited ions are permitted to coalesce into lattice clusters, which clusters are grown, by further deposition, into a large-grain, thin semiconductor film on the substrate. Preferably, the semiconductor-based gaseous compound includes silane gas with dopant atom source gases.

Synthesis of β‐Si3N4 by Chemical Vapor Deposition

Abstract: Beta-type CVD-Si3N4 plates (up to 1.1 mm thick) have been prepared by adding TiCl4 vapor to the system SiCl4-NH3-H2 at deposition temperatures of 1350° to 1450°C, while α-type or amorphous CVD-Si3N4 was obtained without TiCl4 vapor at the same deposition temperature. Three to four wt % 777V was included in the β-type CVD-Si3N4 matrix. The density, preferred orientation, and lattice parameters of β-type CVD-Si3N4 were examined.

The effect of laser annealing on the critical‐current density in Nb3Ge

Abstract: Pulse laser annealing of Nb‐Ge superconducting films grown by chemical vapor deposition produces an increase in critical‐current density, Jc, if the atomic ratio Nb/Ge is less than three. This Jc increase is caused by flux pinning on the nucleated Nb5Ge3(σ) second‐phase particles rather than on grain boundaries in the melted and resolidified surface layer. This resolidified layer is amorphous or highly disordered.

P-N junction and Schottky barrier diode fabrication in laser recrystallized polysilicon on SiO 2

Abstract: P-N junction and Schottky barrier diodes have been fabricated in laser recrystallized polycrystalline silicon on SiO 2 . A repetitively Q-switched Nd3+:YAG laser was used to anneal polysilicon deposited by LPCVD on oxide thermally grown on

Mechanism of condensation of heteroepitaxial A3B5 layers pulse of moderate power

Abstract: The mechanism of condensation of heteroepitaxial layers in laser deposition was studied on GaAs films on NaCl. Films were deposited in a superhigh vacuum using laser pulses of moderate power. Pulsed deposition proved to be more suitable for nucleation and growth than continuous deposition. However in this case it is important to compare the number of atoms deposited per pulse and the number of preferential adsorption centres in the substrate temperature of 310 °C. The density of dislocations in the films was about 109 cm−2. The main reasons for the dislocations are the excess of low volatile component and thermal stresses. Using a laser with quantum energy higher than the energy gap of the deposited semiconductor GaAs, which provides congruent evaporation, and making an additional deposition of As, we could reduce dislocations to 107 cm−2. A mechanism is proposed to explain the reduction of temperature in single crystal growth under laser deposition: high energy ion component of laser plasma gives rise to orienting defects on the substrate surface, and these defects determine epitaxial growth. [Russian Text Ignored].

Apparatus for sensing deposition of a thin film layer of a material

Abstract: Apparatus for sensing deposition of a thin film layer of a material from a source onto a substrate having a carriage assembly including a predetermined number of apertures for selectively passing predetermined portions of a material from the source along each of a plurality of predetermined paths located in the proximity of the substrate under conditions correlated to that under which the material is deposited through a deposition path onto the substrate, inhibiting elements positioned relative to the carriage assembly for selectively inhibiting passage of predetermined portions of the material through a selected number of the predetermined number of the apertures, and a monitior for monitoring a selected parameter of the thin film material which is passed through other than the selected number of apertures of the carriage assembly wherein the monitor includes a plurality of detectors one of each of which is positioned along one of the plurality of predetermined paths and being adapted to sense a predetermined portion of a thin film material being passed along its associated predetermined path and for producing electrical signals derived from the selected parameter representating at least one of the mass per unit area, thickness and deposition rate of the thin film material is shown. A method for measuring at least one of the mass per unit area, thickness and deposition rate of a thin film layer being deposited through a deposition mask selected from a plurality of deposition masks adapted to be positioned between a substrate and a source is also shown.

Investigation of damage to metals by pulsed CO2 laser radiation

Abstract: A study was made of the physical mechanism involved in piercing holes in metallic plates, using CO2 laser radiation. It was established experimentally that the energy consumed in removing a unit volume of a metal has a minimum, depending on the duration and energy of the laser pulse. An explanation is proposed for the laws governing this behavior, based on ideas of the ejection of liquid from a crater by the vapor pressure of the material. The effect on the interaction efficiency of the absorption of laser radiation in the plasma jet is taken into account.

Compact long-life high PRF 722.9 nm neutral lead vapor laser

Abstract: Several new construction techniques for a compact long-life high pulse-repetition frequency (PRF) 722.9 nm neutral lead vapor laser are described. A quartz discharge envelope, coaxial oven, and controlled semiself-heating techniques were employed. An average laser output power of 90 mW at a pulse repetition rate of 5 kHz has been obtained with a discharge efficiency of 0.03 percent.

The Preparation of Optical Surfaces for Thin Film Deposition

Abstract: Very clean surfaces are required for successful vacuum deposition of optical thin films. This paper describes a simple technique which has been developed at NPL for cleaning substrates and discusses its effectiveness. Cleaning procedures used by some other workers are reviewed.

Punching working method by means of laser

Abstract: PURPOSE:To prevent extension of the hole diameter to punch a processed material straightly, by moving the focus position of the pulse laser to hole bottoms successively and by increasing the laser output gradually. CONSTITUTION:The focus position of laser beam 1 of the first pulse laser for processed material 3 is set to a prescribed position on the surface of processed material 3, and the output of the pulse laser is set to a low value. For every irradiation of the pulse laser, the focus position is moved to bottoms of the hole successively, and the output of laser beam 1 is increased gradually or the first irradiation output is set to the lowest output in comparison with the following irradiation output at least. At this time, though oblique-line part 6 of the laser bean is irradiated to the surface of processed material 3, hole 8 is punched without fushion of the surface because the power density on the surface is low.

Method and apparatus for preparing thin film of compound

Abstract: PURPOSE:To form a dense thin film of a compound rapidly in good reproducibility, by a method wherein, while a metal or a semicondutor is vapor deposited on a base plate under high vacuum, ion beam is irradiated onto the base plate while the strength thereof is controlled corresponding to the vapor deposition speed of the aforementioned vapor deposition material to react the vapor deposition material and ion seed on the base plate. CONSTITUTION:An ion seed such as an gaseous O2 or a N2 is supplied into a vacuum tank 2 frorm an ion seed tank 13 through a leak valve 8 in a constant flow amount and, while ionized by an ionizing gun 4 to be accelerated as ion beam, introduced into the vacuum tank 1 from a small hole 5 to be irradiated on the surface of a base plate 9. During this time, vacuum exhaust pumps 11 and 12 are adjusted to lower the pressure of the tank to about 1/100 of the pressure in the tank 2. On the other hand, an evaporation source comprising a metal or a semiconductor is heated by a heating mechanism 3 and the vapor deposition material is vapor deposited on the base plate 9. The vapor deposition substance is reacted with the ion seed on the base plate 9 to form a thin film of the compound, especially, a thin film having an optional composition consisting of the metal or the semiconductor and O2 or N2.

Working method for extremely narrow hole by means of laser

Abstract: PURPOSE:To facilitate the work for an extremely narrow hole, by irradiating the pulse laser to make a hole whose diameter is smaller than the laser beam diameter by forming a laser beam reflective coating layer, where an under-hole is processed, on the surface of the processed material. CONSTITUTION:Coating layer 5 of a high laser beam reflection factor is formed on the surface of processed material 3. At this time, under-hole 6 whose diameter is smaller than the diameter of laser beam 1 is formed in coating layer 5. Next, the output of the pulse laser irradiated to under-hole 6 is set to a low value when the hole is shallow at the initial stage of holing work. Then, base metal fusion region 7 is restrained to a small quantity, and coating layer 5 is not fused under the influence of fusion region 7. The output of the pulse laser is set to a higher value according as the hole is deeper. At this time, base metal fusion region 7 becomes deeper, and coating layer 5 is not fused by the influence of region 7, and thus, a very narrow hole is punched in processed material 3.

Laser Annealing of Ion Implanted Silicon

Abstract: Pulsed laser annealing of ion implanted silicon leads to the formation of supersaturated alloys by nonequilibrium crystal growth processes occurring at the interface during liquid phase epitaxial regrowth. The interfacial distribution coefficients from the melt (k?) and the maximum substitutional solubilities (Csmax) are far greater than equilibrium values. Both k? and Csmax are functions of growth velocity. Mechanisms limiting substitutional solubilities are discussed.

A beam source for deposition of thin film alloys and method therefor

Abstract: The invention is an apparatus and method for achieving thin film deposition, of uniform composition, from evaporated alloys. A source of wire alloy, selected for the particular thin film deposition on a substrate, is continuously fed through a region of high speed electron bombardment confined to an end of the wire, for evaporation of the wire in the vicinity of the substrate. An ion flux detector controls the rate of feeding of the wire source in accordance with the detected flux to lay down a uniform thin film of predetermined thickness. A high potential is established between the wire and the source of the electrons and the liberated electrons are guided by the electric field toward the end of the wire being evaporated, which serves as an anode.

Influences of gas flow on chemical vapor deposition of superconducting Nb‐Ge films

Abstract: Nb‐Ge films, which have been prepared by chemical vapor deposition, have been studied for superconducting transition temperatures, crystal structures, and growth morphology. In the films a relationship was obtained among positions at which the highest Tc films are deposited, the degree of orientation for A15 crystallites is lowered, and the microstructures for film surface change has been found. This can be explained in terms of a higher deposition rate of Ge than that of Nb.