Electrodeposition and pulsed laser deposition for CDTE and Cd{sub}xHg{sub}(1-x)Te thin films

摘要

CdTe and Cd{sub}xHg{sub}(1-x)Te (CMT) thin films were grown by cathodic electrodeposition and pulsed laser deposition (PLD). Ellipsometry, XRD and XPS analysis techniques were used. For Cd{sub}xHg{sub}(1-x)Te samples with 1-x = 0 and ～0.1 were studied. Different concentrations of [Hg{sup}+2] in the electrolyte lead to films with diverse Cd and Hg contents and diverse kind of oxidizing. XPS reveals that a surface layer ～20 A thick of native oxide (TeO{sub}2, CdO, CdTeO{sub}3) is formed after electrodeposition. Hg segregates strongly to the native oxide layer and appears to influence on its amount and nature. For PLD samples of CdTe, a surface oxide layer was only ～8 A thick. For this samples, smaller oxidation and much smaller incorporation of OH{sup}- were observed. XRD reveals that CdTe and CMT are polycrystalline with <111> as a preferential orientation in electrodeposited and PLD samples. PLD technique presents a better crystalline structure when the substrate temperature is increased up to 240°C. This effect is also got by controlling the energy of the laser pulse. Values for Absorption coefficient are similar in both techniques up to 2 eV, then PLD samples get the highest values (near 10{sup}6 cm{sup}-1). The substrate temperature and the energy of the laser pulse are variables that correctly adjusted produce films with absorption curves closer to that of the single crystal. An additional absorption broad structure appear when the substrates are heated to 240°C before deposition