Regulation of Substrate-Target Distance on the Microstructural, Optical and Electrical Properties of CdTe Films by Magnetron Sputtering

Abstract

Cadmium telluride (CdTe) films were deposited on glass substrates by direct current (DC) magnetron sputtering, and the effect of substrate-target distance (Dts) on properties of the CdTe films was investigated by observations of X-ray diffraction (XRD) patterns, atomic force microscopy (AFM), UV-VIS spectra, optical microscopy, and the Hall-effect measurement system. XRD analysis indicated that all samples exhibited a preferred orientation along the (111) plane, corresponding to the zinc blende structure, and films prepared using Dts of 4 cm demonstrated better crystallinity than the others. AFM studies revealed that surface morphologies of the CdTe films were strongly dependent on Dts, and revealed a large average grain size of 35.25 nm and a high root mean square (RMS) roughness value of 9.66 nm for films fabricated using Dts of 4 cm. UV-VIS spectra suggested the energy band gap (Eg) initially decreased from 1.5 to 1.45 eV, then increased to 1.68 eV as Dts increased from 3.5 to 5 cm. The Hall-effect measurement system revealed that CdTe films prepared with a Dts of 4 cm exhibited optimal electrical properties, and the resistivity, carrier mobility, and carrier concentration were determined to be 2.3 × 105 Ω∙cm, 6.41 cm2∙V−1∙S−1, and 4.22 × 1012 cm−3, respectively.

Influence of Various Target to Substrate Distances on the Structural and Optical Properties of Sputtered Gd-Doped ZnO Thin Films

“…The surface roughness shows further decrease to 2.84 nm when the distance is increased to 15 cm. This is resulting from the excess kinetic energy of the Gd and Zn molecules along with significant bombardment that came from the sputtering particles [20]. Referring to the transmittance spectra, it was discovered that transmittance value is over 90 % in the visible range for the distances at 12.0, 13.5 and 15.0 cm.…”

“…These parameters have been investigated by many researchers previously however, no investigation has been done for the properties of Gddoped ZnO at various target to substrate distances. Target to substrate distance is a very important parameter to be determined since the kinetic energy of atoms from substrate could bounce back to target affecting the crystallinity and growth of the films [20]. Thus, this present study aims to prepare a good crystal quality of the films by investigating the influence of target to substrate distance on the Gd-incorporated ZnO by depositing the film simultaneously using sputtering.…”

Role of CdTe Interface Structure on CdS/CdTe Photovoltaic Device Performance

“…Microstructural control of the CdTe films by oblique angle deposition can engineer different crystal structures and crystallite orientations of the polycrystalline thin films. In previous studies, an X-ray diffraction (XRD) analysis of room temperature (RT) GLAD CdTe has been shown to exhibit cubic [19][20][21][22], mixed phase [20], or hexagonal CdTe crystal structures for the films prepared by varying source flux angles from Φ = 0 • to 80 • using different physical vapor deposition techniques, such as thermal evaporation and sputtering [23][24][25][26]. The presence of overlapping cubic and hexagonal phase diffraction peaks implies the mixed phase, with the dominant peaks being the cubic phase.…”