In this study, copper indium gallium diselenide [Cu(In,Ga)Se 2 ; CIGS] films were prepared by selenization of Cu-In-Ga metallic precursors using ditert-butylselenide (DTBSe) under atmospheric pressure. Based on the results of θ-to-2θ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it was found that the films selenized at 300 or 400 • C for 60 min showed the presence of Kirkendall voids along with the XRD signitures of pure copper (Cu) and certain intermediate binary selenides, copper indium diselenide (CIS) and CIGS depending on temperature while only a single CIGS structure was detected in those films selenized at 500 or 600 • C for 60 min. A 5-temperature selenization process was found to enable the formation of CIGS structure with better crystalline quality and thickness uniformity. It is believed that intermediate binary and ternary selenides are formed sequentially with increasing completeness during low-temperature selenization stages of the 5-temperature selenization process. This enhances the subsequent formation of CIGS structure at high-temperature selenization stages of the 5-temperature selenization process with improved structural and morphological properties.Cu(In,Ga)Se 2 is a I-III-VI 2 chalcopyrite semiconductor that has attracted much attention as a promising absorber for photovoltaic devices. Meanwhile, most CIGS films were prepared by physical vapor deposition (PVD) 1 including co-evaporation technique and molecular beam epitaxy (MBE). 2 Other methods such as sputtering, selenization of precursors, 3 solvothermal method, 4 and metallorganic chemical vapor deposition (MOCVD) 5 have also been reported. For simplicity and large-area fabrication, the most common CIGS preparation technique relies on pre-deposition of Cu-In-Ga metallic precursor followed by selenization using Se vapor 6 or H 2 Se gas. 7 Although the selenization of Cu-In-Ga metallic precursor using H 2 Se gas is a convenient approach for large scale CIGS thin film solar cell fabrication, the high toxicity of H 2 Se is a critical issue of safety concern. Therefore, the use of Se vapor is considered as an alternative for the selenization of a CIGS film. However, during the selenization process, it is difficult to incorporate Ga into the CIS structure. Instead of forming a single CIGS quaternary phase, mixtures of CIS, CIGS, CGS or other secondary phases are often formed in the selenized films. Also, a selenization process using Se vapor needs to resort to a vacuum environment which is detrimental to the throughput of CIGS solar cell fabrication.Organoselenides including dimethylselenide [(CH 3 ) 2 Se:DMSe], 8 diethylselenide [(C 2 H 5 ) 2 Se:DESe], 3 and ditert-butylselenide [(C 4 H 9 ) 2 Se:DTBSe] 9 have recently been proposed as alternative choices for the Se source. These organoselenides are liquid at room temperature and are stored in stainless steel container so that they are much safer than H 2 Se which is commonly stored in a high pre...

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A discussion of CMOS readout technologies for infrared (IR) imaging systems is presented. First, the description of various types of IR detector materials and structures is given. The advances of detector fabrication technology and microelectronics process technology have led to the development of large format array of IR imaging detectors. For such large IR FPA's which is the critical component of the advanced infrared imaging system, general requirement and specifications are described. To support a good interface between FPA and downstream signal processing stage, both conventional and recently developed CMOS readout techniques are presented and discussed. Finally, future development directions including the smart focal plane concept are also introduced.

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