Study of the structural and photoluminescence properties of CdTe polycrystalline films deposited by close-spaced vacuum sublimation

Abstract

a b s t r a c tThe polycrystalline CdTe films were deposited by the close-spaced vacuum evaporation at the different substrate temperatures (150-550 1C). The X-ray diffraction measurements of structural and substructural properties of these films were carried out to study their phase composition and texture. The films' parameters such as the coherent scattering domain size, microdeformation level and mean density of dislocations were determined based on the broadening of diffraction peaks. In this case the Hall and three-fold convolution approximations were used. Surface morphology, grain size and growth mechanism of the films were determined by the scanning electron microscopy. The low temperature photoluminescence measurements allowed us to establish the correlation between the point and extended defect structure on the one hand and the growth conditions on the other. As a result, the growth conditions of CdTe polycrystalline films with fairly good crystal and optical quality were determined.

Morphological, structural, compositional properties and IR-spectroscopy of CdSe films deposited by close-spaced vacuum sublimation

“…[24]) on cleaned glass substrates from stoichiometric CdSe powder using the following growth conditions: evaporator temperature T e was kept constant at 973 K, substrate temperature T s was varied from 373 to 873 K and deposition time t was 10 min.…”

“…In order to separate the contributions in physical broadening from the dispersive structure of the films and micro-deformation the Hall approximation was applied [33]. Besides that, micro-strains level and SD size were calculated by the method based on threefold convolution of XRD line [24,25]. Lattice parameters of the wurtzite and sphalerite phases were calculated by the NelsoneRiley extrapolation method [33,34].…”

“…However, wave shaped feT s curve shows two minimums at 570 K and 870 K. Similar behavior of feT s dependencies was observed in Refs. [24,38] in the case of CdTe films. The authors assumed that the minimums on feT s curve could be explained by the change in growth mechanism at corresponding temperatures.…”

“…The modifications of the thermal vacuum deposition method such as hot-wall epitaxy and isothermal close-spaced sublimation allow to obtaining CdSe thin films with improved crystal properties [17e23]. Due to the technical features of the evaporator, close-spaced vacuum sublimation (CSVS) method [24] could be considered as a promising low-cost technique for the deposition of the high crystal quality CdSe thin films. This method is widely used for the deposition of the IIeVI compound thin films under conditions close to thermodynamic equilibrium growth [24e27].…”

“…This method is widely used for the deposition of the IIeVI compound thin films under conditions close to thermodynamic equilibrium growth [24e27]. Unfortunately, this technique doesn't allow to obtain films at room temperature deposition conditions due to the constructional features of evaporator [24]. The possible way of this problem solution is in additional thermal shields' usage.…”