The authors report on a metastable defect observed in pentacene thin films. The defect, which is\ud
characterized by a hole trap at Ev+0.6 eV and attempt-to-escape frequency of 5x1012 s−1, can be\ud
reversibly created/removed under a negative/positive bias voltage applied to the aluminum/\ud
pentacene Schottky diode at room temperature in air. Annealing the sample in vacuum at 360 K\ud
removes the defect and prevents its creation by application of any bias voltage in vacuum.\ud
Considering recent calculations of defects in pentacene the authors assume that the defect is formed\ud
by replacing one of the hydrogen atoms by an oxygen atom (C22 H13 O).Peer Reviewe
Two different kinds of electron spin resonance signals, triclinic and isotropic, are observed in amorphous selenium under photoexcitation at 20 K, their concentration being around 10 20 cm Ϫ3 . At higher temperatures, isotropic centers are converted into triclinic ones. These centers are identified as singly and triply coordinated Se defects. The results present experimental evidence for negative-U centers and valence alternation in amorphous selenium. ͓S0163-1829͑97͒50326-2͔
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R48656 A. V. KOLOBOV et al.
A very thin insulating layer (VTIL) is formed by low-energy Ar-beam bombardment in the surface region of undoped hydrogenated amorphous silicon (a-Si:H). Several experimental techniques have been utilized to determine the optimal argon beam bombardment conditions to prepare electrically reliable VTIL and to investigate its physical properties (thickness, structure, nature, and density of defects). VTILs prepared under such conditions make the leakage current of a-Si:H based semiconductor structures negligible and allow bias voltages of several volts (up to 5 V).
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