An ARXPS study of the passivating layer formed on III‐V surface by an innovative anodic treatment in liquid ammonia

Abstract

AbstractAn innovative treatment of III‐V surface is evidenced in liquid ammonia (NH3 liq). This treatment is performed by a controlled anodic electrochemical process at the interface.1 This control provides a novel and reproducible passivation of the InP surface.1The surface coating prevents the formation of oxides for over a year.1 The low anodic charge (≈1 mC.cm−2 range) spent for the process concurrently involves a weak electrochemical dissolution of InP surface and ammonia oxidation which trigger the passivation process.1 Studies using either cyclic voltammetry or galvanostatic treatment followed by XPS measurements show that the surface is successfully passivated by an ultrathin film associating phosphorus and nitrogen atoms in a quasi‐monolayer structure. Reproducible XPS data indicate that the ratio between nitrogen and phosphorus atoms in the film is close to two. High resolution N1s spectra reveal a double structure of the peaks, indicating that two chemical environments must be considered to describe the nitrogen atoms neighboring in this capping film. Information about the spatial film organization are investigated by angular‐resolved XPS depth profiles analysis. Experiments are performed with a Thermo Fisher Scientific Theta Probe XPS spectrometer which exhibits an innovative ARXPS acquisition mode. The evolution of the respective contributions of P and N or In signals, perpendicularly to the surface, permit to propose a paving of the surface with a polyphospazene like film. Copyright © 2010 John Wiley & Sons, Ltd.