Vapour growth and characterization of beta indium sesquitelluride crystals

• Beta indium sesquitelluride crystals are grown by PVD method.
• XRD analysis confirmed zinc blende structure with beta phase.
• Microhardness at a load of 15 g is 353.5 kg/mm2.
• Resistivity at 300 K is 135.16 Ω cm and activation energy is 0.52 eV.
• Conduction mechanism follows CBH model.

Physical Vapour Deposition (PVD) provides stoichiometric crystals of different morphology, depending upon the materials, geometry of ampoules, temperature profiles, growth parameters and kinetics of crystallization. The crystal forms such as needles, platelets and spherulites of beta indium sesquitelluride (β-In2Te3) were produced by controlling the temperature of source and growth zones. The X-Ray Diffraction (XRD) and chemical analysis of the spherulitic crystals confirmed zinc blende structure with beta phase. Their resistivity (135.16 Ω cm) at room temperature (300 K) was determined by van der Pauw method. The temperature dependence of DC conductivity was investigated using the conventional two-probe technique. The variation of dielectric constant (ε1) and dielectric loss (tan δ) with temperature has been studied for different frequencies (1 kHz–1 MHz). The AC conductivity, σac(ω) was found to vary with angular frequency as ωs, where s is the frequency exponent. The values of s lie very close to unity and show a slight decrease with increase in temperature, which indicate a Correlated Barrier Hopping (CBH) between centres forming Intimate Valence Alternation Pairs (IVAP). The activation energy for conduction ranges from 0.187 eV to 0.095 eV. The microhardness of β-In2Te3 spherulites is found to be 353.5 kg/mm2, which is higher than that of other semiconducting chalcogenides. The results thus obtained on crystals grown from vapour phase open up ample possibilities for radiation detector applications.