Condensation and sublimation of thin amorphous arsenic films studied by ellipsometr

TL;DR

This study uses in-situ ellipsometry to analyze the condensation and sublimation behaviors of thin amorphous arsenic films, providing insights into sticking coefficients and activation energies relevant for material processing.

Contribution

It presents new measurements of arsenic sticking coefficients and activation energies for sublimation, advancing understanding of arsenic film dynamics on GaAs substrates.

Findings

Sticking coefficient on Ga-rich surface: 7x10^-3

Sticking coefficient on amorphous arsenic: 8x10^-4

Activation energy for sublimation: 1.84 eV

Abstract

From in-situ ellipsometric measurements during condensation of As4 molecular beam on GaAs(001) substrate the arsenic sticking coefficient was determined. For the substrate with Ga-rich surface reconstruction at 60C the sticking coefficient was found to be 7x10-3, whereas for the surface of amorphous arsenic this coefficient was only 8x10-4. Kinetic studies of As sublimation were also performed and activation energy for the process was obtained. For amorphous As films grown from As2 beam the activation energy was found to be DeltaE=1.84+-0.03eV, which is 0.39eV higher than the enthalpy of solid-vapor phase transition. Temperature dependence of evaporation coefficient for amorphous As was determined in the 230-290C range.