Growth and Characterization of Large-size InSe Crystal from Non-stoichiometric Solution via a Zone Melting Method

Indium selenide (InSe) is a III-VI group semiconductor with interesting physical properties and wide potential applications in the fields of diodes, photovoltaics, optics, thermoelectrics, and so on.However, the production of large-size InSe crystal is difficult due to the inconsistent melting of In and Se elements and the peritectic reactions between InSe, In6Se7 and In4Se3 phases.In this work, a zone melting method, which has advantages of low cost and solid-liquid interface optimization, is employed for InSe crystal preparation.Because the initial mole ratio of In:Se is of great importance to InSe crystal growth, the non-stoichiometric In0.52Se0.48solution was precisely used for growth based on the peritectic reaction of In-Se system, resulting in a InSe crystal productivity ratio of about 83%.An ingot with dimensions ϕ27×130 mm³ is obtained, with a typical slab-like InSe crystal in the size of 27 mm×50 mm.The successfully peeled cleavage plane exhibits a good single-crystalline character as only (00l) peaks are detected in the X-ray diffraction pattern.The crystal has a hexagonal structure and the elements are distributed uniformly in the matrix.The transmittance is tested at ~55% under 1800 nm wavelength, and its band gap is measured to be ~1.22 eV.The InSe crystal has a maximum electrical conductivity σ around 1.55× 10 2 S• m -1 along the (001) direction and a lowest thermal conductivity (κ) of 0.48 W• m -1 • K -1 perpendicular to the (001) direction at 800 K.These results imply that the zone melting method is indeed an effective approach for fabricating large-size InSe crystal, which could be applied for various studies.The measured electrical and thermal behaviors provide a significant reference for InSe crystal application in the future.