Ellipsometric studies of the natural oxide film on the surface of cadmium telluride

Abstract

It is established by ellipsometric measurements that the interaction process of a sheared surface of single-crystal cadmium telluride with atmospheric air has two stages. In the first 7-10 days, the character of the change of the measured ellipsometric parameters corresponds to the formation of an absorbing layer with a thickness of one or two monatomic layers. Beginning at 20 days, a transparent film appears, possibly an oxide, whose refractive index is close to 2.2, while the thickness increases to 5-6 nm in an oxidation time of up to 1 year. Starting from literature data, it is assumed that the inner film is a layer of free tellurium, while the outer film is formed by cadmium or tellurium oxides or a mixture of them.

Ellipsometric Analysis of Cadmium Telluride Films’ Structure

“…The optical constants of CdTe = 3.04, = 0.29 [16] ( = 632 nm) and refractive index of the oxide layer = 2.23 on cadmium telluride surface [20] were used for computing.…”

Real-Space Mapping of Surface-Oxygen Defect States in Photovoltaic Materials Using Low-Voltage Scanning Ultrafast Electron Microscopy

“…These specimens were firstly immersed into hot (90 ℃) mixed solution of H2SO4 (98%) and H2O2 (30%) with volume ratio 3:1 for 10 minutes, subsequently, they were taken out and put into a 5% HF solution for 30 seconds and washed by deionized water for several times. After that, they were dried with ultrapure N2 and directly transferred into the 45 Based on previous reports, the thickness of native oxide layers on all the selected materials is less than 1 nm when they were exposed to air/ moisture for a short period of time (from hours to days) , [46][47][48] furthermore, all the samples that measured as received in the present work were initially stored in sealed boxes which saturated with Ar and after taken out, they were stored in vacuum chamber so the thickness of less than 1 nm can be guaranteed for the oxide layer. All S-UEM experiments reported here were conducted at a repetition rate of 8 MHz to introduce an interval of 125 ns for successive events, making sure full recovery of the system back to the initial state before the next pulse comes.…”

“…The XPS measurements and argon (Ar) etching were performed by an Axis Supra DLD spectrometer (Kratos Analytical) equipped with a monochromatic Al Kα X-ray source ( h ν = 1486.6 eV) operating at 150 W, a multichannel plate, and a delay line detector under a vacuum of ∼10 9 mbar, as previously reported . On the basis of previous reports, the thickness of native oxide layers on all selected materials is less than 1 nm when these are exposed to air/moisture for a short period of time (from hours to days); − furthermore, all samples that measured as received in the present work were initially stored in sealed boxes that saturated with Ar and after taking out, these were stored in a vacuum chamber so the thickness of less than 1 nm can be guaranteed for the oxide layer. All S-UEM experiments reported here were conducted at a repetition rate of 8 MHz to introduce an interval of 125 ns for successive events, making sure of full recovery of the system back to the initial state before the next pulse comes.…”