Measurement of Partial Pressure over CdSe and CdTe by an Optical Absorption Method

Abstract

Partial pressures of the constituent elements over CdSe(s) and CdTe(s) have been measured by an optical absorption method. One set of measurements used optical cells consisted of an optical path chamber and a sample chamber. Dissociation constants were logK_CdSe=logP_Cd²×P_Se2(atm³)=−33416⁄T+20.43(707∼936°C) and logK_CdTe=logP_Cd²×P_Te2(atm³)=−29979⁄T+19.62(763∼908°C). Using another type of optical cell having also a reservoir chamber, control of partial pressure over the sample (CdSe(s) or CdTe(s)) was attempted by regulating saturated pressure of one of the constituent elements at the reservoir temperature, T_R. When P_iTR (i: Cd, Se₂, Te₂), the partial pressure at the reservoir, is larger than P_i^*, the partial pressure corresponding to the total pressure minimum at a given temperature, partial pressure control is effective with such a reservoir. However, when P_iTR is smaller than P_i^*, partial pressure control by a reservoir is not effective, and the condition of the total pressure minimum dominates in the system.