Spherulitic crystallization of β‐In 2 Te 3 by physical vapour deposition

2017

J Appl Cryst

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The present work demonstrates a novel use of physical vapour deposition for grain‐growth engineering by optimizing supersaturation, which led to the evolution of stoichiometric indium monoselenide crystals, employing a custom‐fabricated dual‐zone furnace. The growth zone was kept at a constant temperature for different experimental runs (673–883 K), while the source zone was kept at a stable temperature of 1123 K. In this way, the temperature difference ΔT = 240–450 K resulted in a significant increase of the mass transport between the zones so as to accomplish bulk crystallization. At comparatively low supersaturation (ΔT = 240 K), the presence of nodules and flakes was observed. When ΔT = 250 K, multiple grains were formed owing to temperature asymmetry at the rough vapour–solid interface. A further increase in supersaturation (ΔT = 330 K) facilitated polyhedral grain growth, with distinct grain boundaries. A subsequent increment in ΔT (400 K) led to evolution of the polycrystalline morphology to well developed hexagonal platelets owing to adsorption of atoms on surface steps and kinks in accordance with the leading‐edge growth mechanism. Energy‐dispersive analysis by X‐rays and X‐ray diffraction experiments were carried out to confirm the structure and phase of crystals. Microindentation studies were done to assess the hardness and mechanical stability of the as‐grown crystals in response to external loads in order to explore their suitability for solar cell applications. The investigations of bulk vapour phase transport, morphology and strengthening of InSe platelets provide pathways for the production of crystalline textures with versatile properties.

Section: Resultsmentioning

confidence: 96%

“…Fig. 7 displays the spherulitic crystallization of InSe owing to enhanced mass transport/concentration gradient, analogous to In 2 Te 3 (Reshmi et al, 2011). The masses of these aggregates grown for two, three and four days are equal to 0.026, 0.037 and 0.045 g, respectively.…”

Section: Figurementioning

confidence: 99%

Grain-growth engineering and mechanical properties of physical-vapour-deposited InSe platelets

Teena

2017

J Appl Cryst

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“…An engineering mechanism was proposed for the preparation of Sb 2 Se 3 nanostructures using this one-step growth process, which improved their band gap at room temperature. Prior to growth, the inner walls of the quartz ampoule were thoroughly cleaned to remove external materials, employing soap water, H 2 SO 4 and deionized water, followed by ultrasonic waves as discussed by Reshmi et al (2011). Furthermore, ultrafine cleaning was implemented in order to remove fine impurity deposits by subjecting the ampoule to nitrogen plasma.…”

Section: Synthesis Processmentioning

confidence: 99%

Facile synthesis of novel antimony selenide nanocrystals with hierarchical architecture by physical vapor deposition technique

Bibin

2019

J Appl Cryst

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Stoichiometric antimony selenide (Sb 2 Se 3 ) nanocrystals have been successfully engineered by a facile physical vapor deposition method, employing a single precursor of polycrystalline Sb 2 Se 3 charge in a closed quartz ampoule under high vacuum without any foreign seed or extraneous chemical elements. This work underscores the efficacy of the vapor deposition process and provides synthetic strategies to scale down bulk Sb 2 Se 3 into novel nanostructures. The morphological evolution of the tailored architecture was examined on micro and nano size scales by scanning electron microscopy and high-resolution transmission electron microscopy. The intrinsic mechanism governing the nanostructure formation is revealed as layer-by-layer growth, related to the unique layered structure of Sb 2 Se 3 . The optical properties of the grown crystals were probed by UV-vis-NIR and photoluminescence tools. The band-gap values of the microfibers, nanorods, nanooctahedra and nanospheres estimated from UV-vis-NIR analysis are found to be 1.25, 1.47, 1.51 and 1.75 eV, respectively. Powder X-ray diffraction, energy-dispersive analysis by X-rays, X-ray photoelectron spectroscopy, Raman spectroscopy and photoluminescence studies confirmed the quality, phase purity and homogeneity of the as-grown nanostructures. The adopted physical vapor deposition method is thus shown to be a simple and elegant route which resulted in the enhancement of the band gap for the Sb 2 Se 3 samples compared with their counterparts grown by chemical methods. This approach has great potential for further applications in optoelectronics.

“…Micro-structure Figure 1 shows the grown platelets of dimensions 8 mm 9 6 mm 9 2 mm, when temperature difference DT = (T S -T G ) was kept at 120°C as described by Reshmi et al [17]. The temperature of the source zone T S = 700°C and that of growth zone T G = 580°C.…”

Section: Composition Morphology Andmentioning

confidence: 99%

60Co Gamma Irradiation and Annealing Effects on Transport Properties of Antimony Telluride Platelets Grown by Physical Vapor Deposition

George

Acta Metall. Sin. (Engl. Lett.)

2015

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Physical vapor deposition method was employed to deposit antimony telluride (Sb 2 Te 3) crystals in a dual-zone furnace. The microstructure, surface topography and composition of samples were characterized using X-ray diffraction, atomic force and scanning electron microscopy. Seebeck coefficient (S\c), electrical conductivity (r\c) as well as power factor (PF) were enhanced for pure Sb 2 Te 3 samples upon annealing, and the samples annealed at 473 K exhibited the highest PF of 3.16 9 10-3 W m-1 K-2 with an enhancement of 22% in the figure of merit (Z). When the delivered dose of 60 Co gamma radiation was increased from 0 to 30 kGy in the stoichiometric crystals, r\c decreased due to the decrease in mobility. As a result of the increase in S, PF and Z improved by 12.11 and 13.7%, respectively, in the 30 kGy gammairradiated crystals. Both R H (B||c) and S\c were positive, suggesting that the prepared Sb 2 Te 3 crystals retained the p-type semiconductivity after these treatments.