Volume 93, Issue 5, 01 March 2003
Index of content:
- DEVICE PHYSICS (PACS 85)
93(2003); http://dx.doi.org/10.1063/1.1542939View Description Hide Description
We study ion-irradiation-induced electrical isolation in n-type single-crystal ZnO epilayers. Emphasis is given to improving the thermal stability of isolation and obtaining a better understanding of the isolation mechanism. Results show that an increase in the dose of 2 MeV ions (up to orders of magnitude above the threshold isolation dose) and irradiation temperature (up to has a relatively minor effect on the thermal stability of electrical isolation, which is limited to temperatures of An analysis of the temperature dependence of sheet resistance suggests that effective levels associated with irradiation-produced defects are rather shallow For the case of implantation with keV Cr, Fe, or Niions, the evolution of sheet resistance with annealing temperature is consistent with defect-induced isolation, with a relatively minor effect of Cr, Fe, or Ni impurities on the thermal stability of isolation. Results also reveal a negligible ion-beam flux effect in the case of irradiation with 2 MeV ions, supporting high diffusivity of ion-beam-generated defects during ion irradiation and a very fast stabilization of collision cascade processes in ZnO. Based on these results, the mechanism for electrical isolation in ZnO by ion bombardment is discussed.
93(2003); http://dx.doi.org/10.1063/1.1543246View Description Hide Description
We have fabricated organic thin-film transistors and integrated circuits based on the small-molecule organic semiconductors α,α′-didecylquaterthiophene, α,α′-didecylquinquethiophene, and α,α′-didecylsexithiophene. The organic semiconductors were deposited by thermal evaporation, with solution-processed and cross linked poly-4-vinylphenol serving as the gate dielectric layer. We have found that bottom-contact devices based on these materials have better electrical performance than top-contact devices, presumably due to more efficient carrier injection from bottom contacts due to the presence of the relatively long alkyl chains substituted at the α- and ω-positions of the oligothiophene molecules. Bottom-contact transistors have carrier mobility as large as 0.5 cm2/V s and on/off current ratio as large as and ring oscillatorsfabricated using bottom-contact transistors and α,α′-didecylsexithiophene as the organic active layer have signal propagation delay as low as 30 μs per stage.