The effects of arsenic doping on the solidification dynamics during pulsed melting of silicon have been studied using the transient conductance technique. At As concentrations below 1 at.%, the incorporation of As into the Si lattice results in negligible differences in the solidification dynamics. Between 2 and 7 at.% As, however, the interface velocity is dramatically modified as the liquid-solid interface crosses the As containing region. These velocity changes are consistent with a reduced melting temperature for Si-As alloys. For concentrations of 11 at.% As, the depression in the melting temperature is sufficient to allow the surface to solidify while considerable melt remains buried within the sample. At 16 at.%, the melting temperature is drastically reduced and internal nucleation of melt occurs prior to normal surface melting.

After low-energy pulsed-laser irradiation of Cu-implanted silicon, a double-peak structure is observed in the Cu concentration profile, which results from the occurrence of two melts. From Cu surface segregation we calculate the depth of the surface melt. Cu segregation near the position of the amorphous-crystalline interface gives evidence for a self-propagating melt, moving from the surface region towards the crystalline substrate. Measurements of As-redistribution and of sheet resistance as a function of laser energy density in As-implanted silicon are consistent with the crystallization model which is derived from the effects as observed in Cu-implanted silicon.

The results imply a large difference in melting temperature, heat conductivity and heat of melting between amorphous silicon and crystalline silicon.

A semi-empirical method to determine the undercooling-velocity relationship for laser induced melting is presented. The technique uses measurements of melt depth versus time to control numerical simulations, resulting in a map of the interface temperature as a function of time, and consequently as a function of the interface velocity. The results are independent of any model for the velocity-undercooling relationship. Results of the technique on simulated and experimental melt depth data are presented. Transient conductance data on 28 nanosecond 694 nm laser irradiation of silicon indicate an undercooling-velocity slope of 17±3 K/(m/sec) near the melting point. Picosecond optical transmission data show a much smaller slope.

We have used time-resolved x-ray diffraction measurements of thermal expansion induced strain to measure overheating and undercooling in <100> and <111> oriented silicon during pulsed laser melting and regrowth. 249 nm (KrF) excimer laser pulses of 1.2 J/cm2 energy density and 25 ns FWHM were synchronized with x-ray pulses from the Cornell High Energy Synchrotron Source (CHESS) to carry out Bragg profile measurements with ±2 ns time resolution. Combined overheating and undercooling values of 120 ± 30 K and 45 ± 20 K were found for the <111> and <100> orientations, respectively, and these values have been used to obtain information on the limiting regrowth velocities for silicon.

In recent years GeSe2 glass has been intensively studied by different methods. Light scattering experiments [1–10] have been used to investigate the molecular structure of the chalcogenide glasses. Diffraction studies [16–17] have shown that the short range order of this glass is similar to that of the crystalline GeSe2. Raman [9–10] and Mössbauer [11–15] spectroscopies have extended these results to include large number of atoms (intermediate range order). Glass-crystalline transition induced by laser irradiation has been investigated essentially by Raman scattering [10–16].

The most predominant ripple properties can be explained by existing perturbative theories. We present experimental results on novel types of ripples, which suggest that theory has to go beyond first-order perturbation and that the material's response is not well understood.

We investigate the effects of Nd:YAG and excimer laser irradiation on the Ge(100) surface under UHV conditions over a temperature range 140 < T(K) < 300 using the surface sensitive probe of He atom diffraction. We study the effects of irradiation on surface damage and order using the apparent (2×1) ࢐ c(2×4) transition. We monitor surface contamination in situ. The temporal thermal response is modeled theoretically to aid in assessing the experimental results. The capability to maintain a Ge(100) surface at low temperatures free of contamination and well ordered is demonstrated.

The temperature dependent competition between solid phase epitaxy and random crystallization in ion-implanted (As+, B+, F+, and BF2+) silicon films is investigated. Measurements of time-resolved reflectivity during cw laser heating show that in the As+, F+, and BF2+-implanted layers (conc 4×1020cm-3) epitaxial growth is disrupted at temperatures 1000°C. This effect is not observed in intrinsic films or in the B+-implanted layers. Correlation with results of microstructural analyses and computer simulation of the reflectivity experiment indicates that disruption of epitaxy is caused by enhancement of the random crystallization rate by arsenic and fluorine. Kinetics parameters for the enhanced crystallization process are determined; results are interpreted in terms of impurity-catalyzed nucleation during the random crystallization process.

The behavior of highly anisotropic materials under short pulses of high power laser irradiation has been studied by irradiating highly oriented pyrolytic graphite (HOPG) with 30 nsec Ruby-laser pulses with energy densities between 0.1 and 5.0J/cm2. Raman spectroscopy has been used to investigate the laser-induced modifications to the crystalline structure as a function of laser energy density of the laser pulse. A Raman microprobe was used to investigate the spatial variations of these near-surface regions. The irradiation of HOPG with energy densities above ~ 0.6J/cm2 leads to the appearance of the ~ 1360 cm-1 disorder-induced line in the first order Raman spectrum. The intensity of the ~ 1360cm-1 line increases with increasing laser energy density. As the energy density of the laser pulse reaches about 1.0J/cm2, the ~ 1360cm-1 line and the ~ 1580cm-1 Raman-allowed mode broaden and coalesce into a broad asymmetric band, indicating the formation of a highly disordered region, consistent with RBS-channeling measurements. However, as the laser energy density of the laser pulses is further increased above 3.0J/cm2, the two Raman lines narrow and can again be resolved suggesting laser-induced crystallization. The Raman results are consistent with high resolution electron microscopy observations showing the formation of randomly oriented crystallites. Raman Microprobe spectra revealed three separate regions of behavior: (i) an outer unirradiated region where the material appears HOPG-like with a thin layer of material coating the surface, (ii) an inner irradiated region where the structure is uniform, but disordered, and (iii) an intermediate region between the other regions where the structure is highly disordered. The changes in structure of the inner region are consistent with the behavior observed with RBS and conventional Raman spectra. The identification of an amorphous carbon-like layer on the outer region is consistent with a large thermomechanical stress at the graphite surface, introduced by the high power laser pulse, and known to occur in metals.

The behavior of dopants in CdTe has been examined by Krogen and DeNobel and others. The n-type material is easy to dope with good electrical activity. The p-CdTe is more difficult to produce with concentration higher than 6×1016 cm-3. For doping levels above this, the electrical activity of the dopant drops sharply and the hole mobility is reduced. The difficulty in doping p-CdTe stems from both strong compensation effects and low solubility of the usual dopant species.

The electron beam pulse method has been applied to annealing phosphorus implanted cadmium telluride. The threshold electron beam energy density necessary to give good electrical activation and mobility have been established in the range between 9.2-10.1 J.cm-2 for doses from 1014-1016 ions cm-2. A sheet resistance as low as 6.32×10 Ω/  and a carrier concentration as high as 3×1018 cm-3 have been obtained. The impurity profile of the annealed samples have been obtained by etching layer by layer with the etching rate calibrated by chemical techniques and the impurity concentration determined by van der Pauw/Hall technique.

We describe a measurement of the transient conductivity induced in amorphous SiO2 during irradiation by an intense and energetic electron beam. Preliminary results of an experiment [1] we performed at the Pulsed High - Energy Radiographic Machine Emitting X Rays (PHERMEX) facility of Los Alamos National Laboratory indicate that a beam of electrons of energy 17.5 MeV, of current density 1 kA/cm2, and of micropulse duration 3 nsec induce in a-SiO2 an electric conductivity 007E 6 × 10-3 (03A9-cm)-1. This value is 15 orders of magnitude larger than the ordinary (ionic) conductivity of the material [2].

The heat flow calculations have been performed to obtain the threshold energies for the melting of Si and Al during pulsed-laser irradiations under various laser conditions. The temperature dependent optical and thermal properties of the solids are deduced from the available experimental data. The melting threshold energies calculated for the solids are within the accuracy of the experimental values.

A dopant redistribution model that has the dopant diffusion equation partially solved analytically before engaging numerical method in its final solution was formulated. The model which included an evaporation loss mechanism for the near-surface dopants was then employed in the theoretical fitting of the measured As and ? redistributed profiles in Si due to single and ten-pulse laser irradiations. All the dopant profiles computed were in good agreement with the measured SIMS data. The values of dopant diffusion coefficients Dℓ in liquid Si that were deduced presently from the dopant profile fitting were (3.2 00B1 0.3) × 10-4-cm2s-1 for As and (4.0 00B1 0.4) × 10-4-cm2s-1 for ? respectively. Comparison to the reported experimental values of Dℓ was also made.

Explosive crystallisation has been observed in deposited a-Ge films irradiated with pulsed Nd-glass laser beam of 400 micro second duration. Transmission electron microscopic examination of the irradiated film shows a polycrystalline region surrounded by radial dendrites of ~ 8-10 ;Cm size. Analysis of the results is consistent with the duplex-melting model of the explosive crystallisation mechanism. Heat released during the amorphous to crystalline transformation of a localised region abruptly crystallises the surrounding area resulting in dendritic growth. The crystallisation is self-sustaining untill the temperature ahead of liquid/amorphous interface drops below 775 K. These results are consistent with earlier study of explosive crystallisation in unsupported a-Ge films and further confirm that the heat loss to the underlying substrate governs the dynamics of the crystallisation process.

In this work, the PEBA induced thermal effects have been varied to study the diffusion of usual implanted impurities (P, As, Sb, In) and segregation phenomena in (100) and (111) silicon. The mean melt-front velocity has been adjusted between 1 and 4 m/s by modifying both the beam fluence and the sample starting temperature. A model for dopant redistribution has been developped, using a mean diffusion coefficient D and solving the one dimensional Fick's equation. Segregation and dopant evaporation are considered and introduced as limit conditions at the liquid-solid interface and at the wafer surface respectively. The impurity redistribution has been experimentally studied by SIMS profiling ; so that interfacial segregation coefificient Ki may be deduced from comparison between experimental and computed profiles.

This paper summarizes the general observations that may be drawn from numerous studies of electronic defects in transient thermally annealed bulk single – crystal silicon and discusses the emerging subjects of electronic defect evaluation in beam – crystallized silicon thin films and in epitaxially – grown III – V semiconductors.

The geometry, origin, and diffusion along hairpin defects in Si were investigated using TEM and SIMS techniques. The defect that grows from the amorphous-crystalline (a/c) interface following solid phase epitaxy growth front was found to be a perfect dislocation with a/2(101) Burgers vector. Misoriented microcrystallites within the a/c transition region are proposed to be nucleation sites for the hairpin dislocations. The density of the crystallites increases with an overall coarsening of the interface which occurs during dynamic annealing processes stimulated by implantation or post-implantation low temperature annealing. Hairpin dislocations were found to pipe-diffuse boron at much higher rates than bulk processes significantly shifting dopant profiles. The diffusion coefficient of boron pipe diffusion at 1150°C was found to be about 104 times higher than the bulk one.

Au/Si Schottky contacts have been used as test structures to investigate defects induced in virgin C.Z (100) N-type silicon after irradiation with a 12 to 20 KeV mean energy electron beam pulse. A thin and highly damaged surface layer was observed from a fluence threshold of 1 J/cm2. In addition electron traps were detected in the PEBA induced melting layer with concentrations in the 1012-1013 cm-3 range. Their depth profiles have been related to the PEBA induced melting layer thickness. Quenching of multidefect complexes is the most probable mechanism for electron trap generation in the processed layer.

A predominant deep level which has an activation energy of 0.4 eV was found to have been formed in the region between the surface and the end-of-range of 200 keV ions. In the fluence range 1012 − 1013cm−2 essentially no difference between the deep level spectra for proton and deuteron bombardments was found.

Studies have been made of n+-GaAs implanted with 300 keV protons to fluences of 1014−1016/cm2. Electrical studies included I–V analysis, DLTS, and thermally stimulated current measurements made on implanted FET-like structures fabricated from MBE GaAs epi-layers. Optical infrared reflectance spectra and high resolution transmission electron micrographs were obtained for as-implanted material and for specimens annealed at 300 °C and 500 °C. Results show as-implanted material can be characterized by a band of traps lying about 0.2 eV below the conduction band with a relatively uniform distribution throughout the implanted region. Thermal processing causes a significant alteration in the density and distribution of these defects.