Browsing by Author "Kumar, Jitendra"

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Development of Al-doped ZnO thin film as a transparent cathode and anode for application in transparent organic light-emitting diodes
(2016-01-01)
Chauhan, Ram Narayan
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Tiwari, Nidhi
;
Anand, R. S.
;
Kumar, Jitendra
;
光電工程學系
Aluminum doped zinc oxide thin films have been prepared by sputtering under argon gas pressure of 0.15 Pa at different radio frequency (RF) power densities to optimize the conditions for application in both bottom emitting and transparent OLEDs. The films exhibit a wurtzite-type hexagonal structure with the [0001] preferred orientation and optical transmittance of better than 80% in the visible region, but, varying energy bandgap. The sputtering at a high RF power density of 2.47 W cm(-2) yields Al-ZnO films of minimum resistivity (similar to 1 x 10(-3) U cm) and high work function (similar to 4.44 eV), appropriate for the anode in bottom emitting OLEDs. On the other hand, AZO films obtained at the low RF power density of 0.31 W cm(-2) correspond to a low work function (3.90 eV) with slightly higher electrical resistivity (5.60 x 10(-3) U cm), useful for cathodes in transparent OLEDs. The comparable performance observed for OLEDs fabricated with AZO and ITO anodes demonstrates the suitability of AZO as an alternative electrode. The increase in RF power density during sputtering leads to perceptible damage of the organic layer. The introduction of a buffer layer of Alq3/LiF/Al just above the organic layer is shown to suppress the damages significantly and improve the performance of the transparent OLEDs.
Silicon induced stability and mobility of indium zinc oxide based bilayer thin film transistors
(2016-11-14)
Chauhan, Ram Narayan
;
Tiwari, Nidhi
;
Liu, Po-Tsun
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Shieh, Han-Ping D.
;
Kumar, Jitendra
Indium zinc oxide (IZO), silicon containing IZO, and IZO/IZO: Si bilayer thin films have been prepared by dual radio frequency magnetron sputtering on glass and SiO2/Si substrates for studying their chemical compositions and electrical characteristics in order to ascertain reliability for thin film transistor (TFT) applications. An attempt is therefore made here to fabricate single IZO and IZO/IZO: Si bilayer TFTs to study the effect of film thickness, silicon incorporation, and bilayer active channel on device performance and negative bias illumination stress (NBIS) stability. TFTs with increasing single active IZO layer thickness exhibit decrease in carrier mobility but steady improvement in NBIS; the best values being mu(FE) similar to 27.0, 22.0 cm(2)/Vs and Delta(Vt)h similar to -13.00, -6.75V for a channel thickness of 7 and 27 nm, respectively. While silicon incorporation is shown to reduce the mobility somewhat, it raises the stability markedly (Delta V-th similar to -1.20V). Further, IZO (7 nm)/IZO: Si (27 nm) bilayer based TFTs display useful characteristics (field effect mobility, mu(FE) = 15.3 cm(2)/Vs and NBIS value, Delta V-th = -0.75V) for their application in transparent electronics. Published by AIP Publishing.