The dielectric function of phase-change materials (PCMs) presents a tremendous difference for the amorphous and crystalline states. Therefore, the measurement of the mid-infrared transparency of thin films of PCMs will provide a cost-efficient method to reveal the dependence of amorphous-crystalline phase transition on their compositions. Although Sb–Te–Se system has shown the advantages of the high speed, low power consumption and long retention life, the information on the mid-infrared transparency of Sb–Te–Se thin films is still insufficient. In our investigation, combinatorial materials libraries of Sb–Te–Se thin films were synthesized. The composition and mid-infrared spectral transmittance of each pixel of Sb–Te–Se thin film in the library were characterized using the energy dispersive X-ray analysis (EDX) and Fourier-transform infrared (FTIR) spectrometer, respectively. The in-depth chemical composition for randomly selected pixels was identified using secondary ions mass spectroscopy (SIMS). The crystallographic structure of some pixels was also identified using micro-area X-ray diffraction (μ-XRD). It can be found that, with the change of composition in Sb–Te–Se thin films, their mid-infrared spectral transmittance can be organized into three distinctive groups, corresponding to amorphous Sb–Se, Sb 2 Se 3 orthorhombic structure and Sb 2 Te 3 rhombohedral structure, respectively. Therefore, the amorphous-crystalline phase transition and the phase-change from the orthorhombic structure of Sb 2 Se 3 to the rhombohedral structure of Sb 2 Te 3 can be completely reflected in the mid-infrared spectral transmittance of Sb–Te–Se thin films.
Wang J.,Ou X. L.,Zhang J.,Chen X. Y.,Zhao K.,Yang X. S.,Zhao Y.
Fe(Te,Se) is a simple, iron-based compound that is conducive to the study of superconductivity mechanisms and has potential for large-scale applications. At present, Fe(Te,Se) thin films are primarily prepared using the pulsed laser deposition method. Herein, FeTe 0.6 Se 0.4 films were grown by magnetron sputtering on CaF 2 substrates. The effect of sputtering pressure on the superconductivity of the film was investigated. Excessive pressure caused a higher iron content, which affected the superconductivity and prevented it from completely reaching a zero-resistance state. Δ T c was smaller for the film grown under 0.2 Pa, and its upper critical field reached 144.35 T, which indicates its greater application potential. Our results illustrated that sputtering pressure was a critical process parameter, which provided an important reference for future research to fabricate commercial iron-based superconducting tapes by magnetron sputtering.
Zhongdong Zhao,Yihan Qi,Qiuying Chen,Xuerong Zheng,Qiuyan Hao,Wen Zhang,Jing Mao,Caichi Liu,Hui Liu
Compared with the expensive and complicated vacuum techniques, the solution-based process to deposit I-III-VI 2 chalcogenide thin films (I=Cu, III=In or Ga, VI=S or Se) has attracted great interests due to its lower cost, higher scalable production and better application in flexible substrate . Herein, a low-toxic and high-active mixture solvent comprised of 1, 2-ethanedithiol and 1,2-ethylenediamine is utilized to dissolve elemental Cu, In and S powders at 60 °C, forming the CuInS 2 (CIS) precursor solution . After spin coating and annealing in a both Ar gas and selenium atmosphere, a dense and large-grained chalcopyrite CuIn(S,Se) 2 (CISSe) thin films with a close-packed grain size of ~800 nm are prepared, eliminating a undesired fine fine-grained bottom layer. In addition, the selenization temperature of the CISSe thin films is also discussed, which influences the phase composition, crystallinity and morphology of CISSe thin films. Photovoltaic device of the CISSe-based thin films is fabricated, obtaining a power conversion efficiency of 6.2% with an active cell area of 0.5 cm 2 under AM 1.5 illumination.
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