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We investigate the electrical properties of ZnO thin-film transistors (TFTs) under the ultraviolet (UV) light illumination to clarify the device reliability. The ON/OFF current ratio of ZnO TFTs shows an evident reduction due to the creation of UV photo-induced current. This behavior degradation becomes severe for devices exposed to a short-wavelength UV light. The persistent photoconductivity is observed in ZnO TFTs under the UV illumination with a much slower decay for the ON-state than the OFF-state, which is attributed to the reduced recombination under a positive gate bias. The UV light instabilities of ZnO TFTs can be explained on the basis of UV photoexcited oxygen vacancies. A feasible mechanism model is proposed in this paper. These observations and analytical model not only provide useful physical insight into the device behaviors, but also offer basic design guideline for oxide TFTs. [ABSTRACT FROM PUBLISHER]

Aims: This study is to assess cognitive function in patients with spinocerebellar ataxia types 1, 2 and 3 (SCA1, SCA2 and SCA3)., Methods: We performed neuropsychological examinations on 8 SCA1 patients, 2 SCA2 patients, and 8 SCA3 patients, as well as 32 healthy subjects matching these patients in age, gender, nationality, and years of education. The neuropsychological examinations were focused on testing executive functions, visuo-spatial perception and verbal memory, attention, immediate and delayed recall, logical thinking function and orientation function., Results: SCA1 patients had significantly impaired executive function, visuo-spatial perception, and attention compared to healthy subjects. Cognitive disorders such as immediate and delayed recall, executive function and verbal memory were observed in SCA2 and SCA3 patients, while attention and visuo-spatial function were not affected. The severity of motor impairment was determined using the international cooperative ataxia rating scale, the scores of which ranged from 11 to 78. The number of patients with mild ataxia, moderate ataxia and severe ataxia was 3, 11, and 3, respectively, with the most severe ataxia occurring on a patient with SCA1. The scores of activities of daily living scale ranged from 20 to 66., Conclusions: Our results showed that mild executive dysfunction occurred in patients with SCA1, SCA2 and SCA3, and verbal fluency and word memory dysfunctions were detected in patients with SCA2 and SCA3. In addition, we found that the decreased logical thinking function and orientation function were observed in patients with SCA1, SCA2 and SCA3. The cognitive status was correlated with the clinical severity of ataxia symptoms rather than age, age of onset, years of education and the duration of disease.