ArF laser etching of n-GaAs (100) in Cl2 gas ambient has been investigated as a function of laser fluency and the main thermodynamical parameters of the process (pressure, temperature and gas phase composition). Experimental results indicate that GaAs laser etching in the presence of Cl2 occurs by a combination of thermally and photochemically initiated reaction steps. The etch rate was found to be kinetically controlled by the surface reaction between photogenerated CI adatoms and GaAs, with an activation energy of 6.3 Kcal/mol. Vertical etch profiles with smooth bottom surfaces were obtained at substrate temperatures above 150°C, low Cl2 partial pressures (≤ 1.5 m Torr), and low laser fluences (≤ 25 mJ/cm2) for etch masks parallel to the | 01 1 | direction.

a-Si:H/a-A11−xOx superlattice structures have been fabricated by ArF excimer laser MOCVD. Periodic variation of composed elements in multilayers with quite uniform layer thickness was clearly shown by SIMS analysis. Optical band gap was increased with the decrease of the well layer thickness, indicating the quantum size effect. With the advantage of the inherent digital process, very sharp interface was obtained, which was confirmed by both XPS and cross sectional TEM analyses.

Photolysis of Si2H6 by an ArF excimer laser has been used to deposit Si homoepitaxial layers at temperatures as low as 300°C. The chemical vapor deposition process at growth rates from 0.5-4 Å/minute is performed in an ultra-high vacuum chamber which, along with an ex situ HF dip and a novel in situ hydrogen clean using laser excitation, results in minimization of oxygen and carbon contamination which inhibits Si epitaxy. The growth involves photolytic decomposition of Si2H6 and the generation and adsorption of SiH2 precursors on the hydrogenated Si surface, which is the rate limiting step. Growth rates are observed to vary proportionally with laser power. Very low defect density films in terms of stacking faults and dislocation loops (less than 105 cm−2), and excellent crystallinity have been deposited as confirmed by Schimmel etching and Nomarski microscopy, transmission electron microscopy, electron diffraction and in situ reflection high energy electron diffraction.

A systematic study of the composition of metal films thermally deposited by laser heating (cw 514 nm) of the group VI hexacarbonyls is described. The films are found to contain significantly lower levels of carbon and oxygen than photochemically deposited films, and are spatially inhomogeneous. Estimates of temperature to determine the extent of laser heating permit the kinetics of this process to be compared to ∞ desorption from single crystal surfaces.

Y2O3 pressed powders were ablated by pulses from a XeCl excimer laser, operating at 308 nm, 150 mj/pulse, ≈15 nsec/pulse and 20 Hz. Emission spectra from Y∗ and YO∗ were recorded as a function of ambient oxygen pressure in the range 10−5 − 4×10−1 Torr, at a laser fluence of ≈ 4 J/cm2. A kinetic model is developed to describe the results, and the application to production of laser-deposited high-temperature superconductor thin films is discussed.

We have deposited CdS thin films onto substrates such as glass, sapphire and high Tc YBCO superconducting films by Nd:YAG laser evaporation in a vacuum environment. X-ray diffraction, optical and electrical measurements were used to study the deposited CdS films. The films are highly oriented with c-axis perpendicular to the surface and are optically smooth. The effects of laser fluence, substrate temperature on the film quality will be discussed. Additionally, Indium doped CdS films were also grown on sapphire substrates by laser deposition. In-situ resistivity measurements were employed to study the film formation process during laser deposition. A simple model was given to explain the in-situ resistivity data. Finally, a deposition temperature window was found to produce good quality CdS/YBCO heterostructures. The superconducting transition temperature of the YBCO films was degraded to 68K from an original Tc of 85 K after CdS deposition. The degradation of the superconducting properties was found mainly due to the interactions in the interface region.

An ArF excimer laser MBE system specially designed for the deposition of ceramic thin films was used to construct atomi-cally defined epitaxial SrCuO2−x films. According to XPS analysis, Cu valence was evaluated to be 2+ in the film as-grown in the presence of 10−7 Torr NO2, but it was less than 2+ in the film prepared in the presence of 10−7Torr 02. In situ XPS depth analysis of as-grown SrCuO2−x film on SrTiO3 substrate revealed the band profile at the interface of the film and substarte. Ceramic superlattices composed of metallic SrCuO2−x (3∼8nm thick) and insulative SrTiO3 (8nm thick) were prepared by sequential heteroepitaxial growth.

Thin films of barium titanate (BaTiOs) have been deposited by pulsed-laser ablation onto (001)-oriented MgO substrates. The films were epitactic as evidenced by both x-ray diffraction and ion-channeling techniques. The film surface appeared smooth and contained a low density of particulates. This latter feature is believed to be due to the formation of target pellets having a very high density.

Good quality ceramic thin films of yttria-stabilized zirconia (YSZ), MgO, BN and TiN were grown on single crystal silicon with (100) orientation using in-situ pulsed laser physical vapor deposition (LPVD) technique.Laser deposition parameters were optimized and the resulting thin films were characterized by X-ray diffraction ,Rutherford backscattering spectrometry and transmission electron microscopy (plan and cross section). All the films were found to be polycrystalline with a texture. The absence of interfacial reaction and smooth interface on the atomic scale are the main features observed in these oxides and nitrides thin films on Si (100) substrate.

Pulsed laser ablation (PLA) is an emerging technology that provides a mechanism to deposit lubricious films and to tailor film properties by the appropriate choice of substrate materials, deposition parameters and post deposition treatments. The properties of MoS2 films deposited by PLA are evaluated as a function of: (1) substrate material, (2) duration of post deposition annealing treatments using 248 nm laser radiation and (3) substrate temperature during deposition. The chemistry and crystal structure of the different films are determined using small angle X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). The tribological properties of the films are then evaluated as a function of their chemistry and crystal structure.

Thin ceramic films (A12O3 ZrO2, Si3N4, and BN) have been prepared by ion beam assisted deposition (IBAD) and their mechanical properties examined. The films exhibit extreme ductility and adhesion, with the former property possibly attributed to the very fine grained, quasi-amorphous grain structure noted for low temperature IBAD coatings.

The laser-induced changes in the hexagonal boron nitride targets that are used in the deposition of pulsed laser-deposited cubic boron nitride films are examined. Although the structure of the hexagonal boron nitride in the irradiated areas is unaltered, the surface morphology changes considerably. Boron-rich spheroids were found to cover the irradiated area. Their origin is consistent with the hydrodynamic sputtering of the hexagonal boron nitride targets, and a liberation of nitrogen atoms to the gas phase.

Zr3Al is an ordered f.c.c. alloy of the L12 type, which under various irradiation conditions can be disordered and then eventually amorphized. In the present transmission-electron-microscopy (TEM) investigation, the nature of the damaged regions formed in individual collision cascades was investigated using low fluence (< 1 × 1011 ions cm−2) bombardments at 290 K with 15 − 120 keV 63Cu ions.

Imaging under dynamical conditions with the fundamental 111, 200, 220 and 113 reflections revealed damaged regions (5.1 - 8.1 nm average diameter) that exhibited black-white strain contrast features. These damaged regions have essentially a spherically symmetrical strain field and probably are three-dimensional clusters of point defects. Imaging with 110 superlattice reflections revealed additional damaged regions (2.4 - 3.7 nm average diameter), which appeared as black spots, that represent disordered regions in the ordered lattice. For both the strain-contrast regions and the disordered regions, as the incident ion energy increased, the number of damaged regions produced per incident ion increased and the fraction of the theoretical collision cascade volume occupied by these regions decreased.

The material-dependent manner in which ion damage occurs in AlAs/GaAs heteroepitaxial structures is demonstrated using conventional and high resolution transmission electron microscopy. Both 150keV and 2MeV Si+ ion implants are employed over a wide range of ion doses. Under conditions which yield rapid build-up of lattice damage in GaAs, the AlAs is found to be relatively resistant to structure breakdown. Indeed, the crystalline AlAs exerts a novel protective effect on immediately adjacent regions of the GaAs layers. For high implantation doses amorphous-crystal superlattices are formed in multilayer structures. For the highest ion doses the AlAs lattice begins to be disrupted by a characteristic, boundary-dependent, heterogeneous mechanism. These observations suggest that mobile point defects play a significant role in AlAs in situ restructuring processes.

The formation of bubbles during high dose implantation of oxygen into silicon, and the subsequent transformation of the bubbles during annealing, were studied with transmission electron microscopy (TEM). There was a threshold for bubble formation at a minimum dose of 0.3 × 1018 oxygen/cm2 and a lower temperature of 550°C. As dose increased the bubbles grew larger and the bubble trails lengthened. However, increasing beam current by a factor of 10 or increasing temperature to 700°C did not affect bubble formation. Bubble evolution during intermediate temperature annealing was also studied using TEM techniques. For 2 hour anneals between 1000 and 1100°C the oxygen bubbles transform into SiO2 particles by first forming a “shell” of SiO2, which then facets, grows inward, and finally completely transforms the bubble into an oxide particle. At temperatures greater than 1100°C the oxide particles dissolve by outdiffusion of the oxygen to the wafer surface.

The alloy system Six(SnyC1-y)1-x was investigated. In this work, samples were prepared by co-implantation of tin and carbon ions into silicon wafers with dosage range 1015 − 1016cm−2, followed by rapid thermal annealing. Rutherford backscattering channeling, Auger sputter profiling, and secondary ion mass spectrometry were employed to study the crystallinity, chemical composition and depth profiles. A near perfect crystallinity for 0.5% at. of tin and carbon was achieved. To study the electrical properties in the implanted materials, diode I-V measurements were performed. The data show near ideal p-n junctions in the co-implanted region. This work demonstrates promising features of group IV semiconductor synthesis by ion implantation.

Ag+ ions were implanted in silica glass at an acceleration energy of 1.5MeV. It is found that Ag atoms are present in both the metallic and ionic states. Ag atoms in the metallic state increase when the Ag atom concentration increases. It is shown that the structure of damaged glass recovers monotonically from the surface to the inside of the glass. The state of the Ag atoms does not depend on the glass structure damaged by ion implantation.

High dose ion implantation followed by solid phase epitaxy has been investigated for use in the synthesis of defect-free graded alloys of Si1−xGex. Two implanted alloy systems were studied: (i) 200 keV 74Ge into <001> Si to form Si-rich alloys and (ii) 150 keV 29Si into <001> Ge to form Ge-rich alloys. After regrowth by solid phase epitaxy the Ge-rich alloys are strained in tension while the Si-rich alloys are in compression and, as a result, strain relaxation is anticipated above a critical dose. We report that solid phase epitaxy at 550°C following implantation of Si into <001> Ge at an energy of 150 keV allowed the defect-free regrowth of alloys with peak concentrations of 11 ± 2 at. % Si (fluence of 7.7 × l016/cm2). Ge was implanted at 200 keV into <001> Si to a peak concentration of 7 at. % (fluence of 3.6 × l016/cm2) and was regrown without the introduction of defects whereas samples implanted to a peak concentration of 13 at. % (fluence of 5.3 × l016/cm2) contained a high density of stacking faults. These experimental observations are compared to theoretical predictions that are based on the strain energy approach.

The self annealing phenomenon was studied utilizing 1 cm diameter, 1 μm thick, <100> oriented silicon films. Previous results established the viability of the self annealing process for medium energy argon beams incident on similar targets [1]. In the current work, doubly aligned backscatter spectra were obtained to improve the sensitivity of the residual lattice damage measurements. In addition, some implantations were performed at elevated temperatures to independently determine the effect of the flux and the sample temperature on the self annealing process. The results showed strong correlations between the implantation flux, sample temperature and the residual lattice damage. Two distinct temperature regions were observed above and below 330 °C with corresponding activation energies of 1.5 eV and 0.1 eV.

We have studied Separation by IMplantation of OXygen (SIMOX) processes using very high dose rates (40–60 μA/cm2). For a dose of 4 × 1017 O+/cm2 at 160 keV, the structure formed by implantation at 50 μA/cm2 is very similar to that associated with lower dose rates. The same dose implanted at a dose rate of 60 μA/cm2, however, results in the formation of pits in the silicon surface as well as a somewhat different oxide structure. Implantation through a surface oxide layer appears to result in a structure similar to that associated with lower dose rate implantation. These and higher dose samples suggest that the threshold for pit formation is related to both dose rate and dose.