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Published online by Cambridge University Press: 17 March 2011
Experimental results on the electronic properties of conditioned Cr/hydrogenated amorphous silicon (a-Si:H)/V thin film devices are presented. The devices under test were electro-formed, and had resistances in the range from several hundred ohms to several kiloohms. The current of conditioned devices varied non-linearly with the bias at low voltages, but exhibited ‘jumps' at a threshold voltage (Vth) (typically 2∼3V ), leading to a resistance change of 1∼3 orders of magnitude. Above Vth the current increased almost linearly with bias, and the carrier transport changed from a semiconducting behaviour into a more conducting (metallic) state. The threshold voltage Vth was found to decrease with increasing temperature and disappear at 340 ∼ 350K, but recovered on reducing the temperature. The transition at Vth has been analysed in terms of electrothermal mechanism. The calculated turnover temperature is about 346K, close to that for the disappearance of Vth. We suggest that the observed transition could involve vanadium oxides such as VO2.