S. U. Campisano

Bio: S. U. Campisano is an academic researcher from University of Catania. The author has contributed to research in topics: Amorphous solid & Silicon. The author has an hindex of 15, co-authored 44 publications receiving 1344 citations.

A melting model for pulsing‐laser annealing of implanted semiconductors

Abstract: The transition to single crystal of ion‐implanted amorphous Si and Ge layers is described in terms of a liquid‐phase epitaxy occurring during pulsing‐laser irradiation. A standard heat equations including laser light absorption was solved numerically to give the time evolution of temperature and melting as a function of the pulse energy density and its duration. The structure dependence of the absorption coefficient and the temperature dependence of the thermal conductivity were accounted for in the calculations. In this model the transition to single crystal occurs above a well‐defined threshold energy density at which the liquid layer wets the underlying single‐crystal substrate. Experiments were performed in ion‐implanted amorphous layers of thicknesses ranging between 500 and 9000 A. The energy densities of the Q‐switched ruby laser ranged between 0.2 and 3.5 J/cm2; time durations of 20 and 50 ns were used. The experimental data are in good agreement with the calculated values for the amorphous thickness–energy−density threshold. The model deals mainly with plausibility arguments and does not account for processes occuring in the near‐threshold region or below the melting temperature.

Arsenic diffusion in silicon melted by high‐power nanosecond laser pulsing

Abstract: The time evolution of temperature and melting in amorphous silicon layers laser irradiated was calculated numerically. Experiments were performed in Si crystals implanted with 400‐keV As to a dose of 5×1015/cm2 and illuminated with 50‐ns‐duration Q‐switched ruby laser pulse in the energy range 1.0–3.0 J/cm2. Comparison between experimental and calculated results allows a quantitative understanding of the amorphous–to–single‐crystal transition. A good agreement was found between the experimental As profiles after laser irradiation and those calculated with a diffusion coefficient of 10−4 cm2/s for As in liquid silicon.

Orientation and velocity dependence of solute trapping in Si

Abstract: Interface segregation coefficients have been measured for Bi in Si for melt growth as a function of velocity for (111) and (100) crystals. Surface layers were melted by ruby laser irradiation and liquid‐solid interface velocities varied from 0.8 to 5 m/s by changing Si substrate temperatures or laser pulse length. Segregation coefficients are strongly dependent on velocity and orientation in this range.

Segregation Effects in Cu-Implanted Si after Laser-Pulse Melting

Abstract: Cu-implanted Si crystals were irradiated with $Q$-switched ruby-laser single pulses. After irradiation with energy density in excess of 1.0 J/${\mathrm{cm}}^{2}$, the Cu atoms accumulate at the sample surface. Thermal annealing in the 500-800\ifmmode^\circ\else\textdegree\fi{}C range casues a migration of Cu inside the specimen, in agreement with diffusion coefficient and solid solubility values. The results indicate the formation of a liquid layer induced by laser irradiation. The solid-liquid interface movement during freezing qualitatively justifies the observed surface accumulation.

Solute trapping by moving interface in ion‐implanted silicon

Abstract: Experiments are reported for Te and Ag implantation in silicon, as examples of slow and fast diffusers, after furnace or laser annealing. Slow diffusers are substitutionally located at concentrations in great excess of the maximum solid solubility after both processes. Fast diffusers inhibit the solid‐phase epitaxial regrowth or are rejected at the sample surface after laser irradiation. Although the epitaxial growth occurs with velocities which differ up to ten orders of magnitude after furnace or laser annealing, the supersaturation is interpreted as due to the same basic mechanism: solute trapping at the moving interface when the residence time is larger than the one monolayer regrowth time. This process is controlled by the diffusion coefficient in the two adjacent phases.

Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV

Abstract: We report values of pseudodielectric functions $〈\ensuremath{\epsilon}〉=〈{\ensuremath{\epsilon}}_{1}〉+i〈{\ensuremath{\epsilon}}_{2}〉$ measured by spectroscopic ellipsometry and refractive indices $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{n}=n+ik$, reflectivities $R$, and absorption coefficients $\ensuremath{\alpha}$ calculated from these data. Rather than correct ellipsometric results for the presence of overlayers, we have removed these layers as far as possible using the real-time capability of the spectroscopic ellipsometer to assess surface quality during cleaning. Our results are compared with previous data. In general, there is good agreement among optical parameters measured on smooth, clean, and undamaged samples maintained in an inert atmosphere regardless of the technique used to obtain the data. Differences among our data and previous results can generally be understood in terms of inadequate sample preparation, although results obtained by Kramers-Kronig analysis of reflectance measurements often show effects due to improper extrapolations. The present results illustrate the importance of proper sample preparation and of the capability of separately determining both ${\ensuremath{\epsilon}}_{1}$ and ${\ensuremath{\epsilon}}_{2}$ in optical measurements.

Channeling and related effects in the motion of charged particles through crystals

Abstract: The motion of energetic charged particles inside a monocrystalline solid can be strongly influenced by channeling and blocking effects. The present article reviews the theory, the experimental studies, and some of the applications of these effects. The coverage of the published literature extends through June 1973.

Model for solute redistribution during rapid solidification

Abstract: A microscopic model for impurity uptake at a sharp crystal‐liquid interface during alloy solidification is presented in terms of the bulk properties of the liquid and solid phases. The results for stepwise growth and continuous growth at the same interface velocity differ quantitatively but exhibit the same qualitative features. A transition from equilibrium segregation to complete solute trapping occurs as the velocity surpasses the diffusive speed of solute in the liquid. The location of the transition varies little with equilibrium segregation coefficient, and a kinetic limit to solute trapping is found to be quite unlikely. Comparison is made with other models; critical differences are pointed out. Coupled with a growth velocity equation and with macroscopic heat‐ and solute‐diffusion equations, the model forms a complete description of one‐dimensional crystal growth. The steady‐state solution to this system is indicated for the case of a planar interface. The results are applied to describe regrowth from laser‐induced melting. Preliminary comparison with experiment is made. The steady‐state solution for thermal and impurity transport is suggested for use whenever detailed computer calculations are unavailable or are unnecessarily involved.