Cadmium selenide thin-film transistors

Abstract

Vacuum-deposited CdSe thin-film transistors (TFT’s) with reproducible good stability, performance, uniformity, and yield were made using sputtered SiO2 gate insulator, Cr source–drain (s–d) electrodes, and postdeposition annealing in N2. These materials and procedures permit the use of multiple pumpdown fabrication methods with no loss in ac characteristics and little sacrifice in dc stability. Promising results were obtained using photolithography (PL) to delineate s–d electrodes, further simplifying fabrication. The dc instability is electron-trapping type and the drain current decay exhibits a logarithmic time dependence. The slope of this decay curve is used as a parameter to describe device stability and its dependence on the fabrication methods studied: M=0.03–0.06 for one-pumpdown devices, 0.05–0.08 for multiple pumpdown TFT’s, and 0.1–0.2 for TFT’s with PL-delineated s–d electrodes. Preliminary reliability studies show that suitably encapsulated TFT’s have long time stability comparable to the good short time stability observed for fresh devices, indicating the absence of built-in failure mechanisms and the capability for a satisfactory operating life.

Electrical, photo-electrical, optical and structural properties of CdSe thin films deposited by thermal and e-beam techniques

“…Furthermore, identification of the appearing crystalline peaks confirmed that both the cubic and the hexagonal phases of CdSe exist in all the deposited films. Peak positions and relative intensities are in very good agreement with the results noted in the JCPDS-IDCC files [19] and previous works [17,20]. Any additional peak which does not belong to one of those phases exists in the diffractograms.…”

Electrical Transport and Grain Growth in Solution-Cast, Chloride-Terminated Cadmium Selenide Nanocrystal Thin Films

“…The nanocrystalline films prepared in this work are comparable to polycrystalline thin films of CdSe formed by evaporation and electrodeposition. 44 , 49 − 52 These films have electron mobilities ranging from 3 to 100 cm 2 /(Vs) and carrier concentrations ranging from 10 11 to 10 18 cm –3 , which are sensitive to the grain size, annealing temperature, and are enhanced by doping with indium. 47 , 53 , 54 In these studies, the grain size in the high-performance materials approaches 100 nm; however, our work clearly demonstrates that strong electronic coupling between nanocrystalline grains (<5 nm) can reliably produce films with comparably high carrier mobilities (10–20 cm 2 /(Vs)) and low carrier concentrations (10 16 cm –3 ).…”

Deposition of silica-silver nanocomposites by magnetron cosputtering

“…These techniques allow, in principle, the growth of high purity homogeneous films with thickness from a few tens of nanometers up to the microme-ters range and with controlled metal atomic fractions in a wide range. Although O 2 is commonly added to Ar to obtain high quality SiO 2 films by rf sputtering of SiO 2 targets, 9 Author to whom correspondence should be addressed; Viale Università, 2-35020 Legnaro (PD), Italy; electronic mail: vomiero@lnl.infn.it addition when Ag and SiO 2 are cosputtered has been reported only for films with thickness in the nanometer range to our knowledge. 5,6 Sputter deposition has also been used.…”