ABSTRACT
This paper reports on the thin film transistor (TFT) based on TiOx prepared by direct current (DC) magnetron sputtering for the application of n-type channel transparent TFTs. A ceramic TiOx target was prepared for the sputtering of the TiO2 films. The structural, optical, and electrical properties of the TiO2 films were investigated after their heat treatment. It is observed from XRD measurement that the TiO2 films show anatase structure having (101), (004), and (105) planes after heat treatment. The anatase-structure TiO2 films show a band-gap energy of approximately 3.20 eV and a transmittance of approximately 91% (@550 nm). The bottom-gate TFTs fabricated with the TiO2 film as an n-type channel layer. These devices exhibit the on-off ratio, the field-effect mobility, and the threshold voltage of about 10(4), 0.002 cm2/Vs, and 6 V, respectively. These results indicate the possibility of applying TiO2 films depositied by DC magnetron sputtering to TiO2-based opto-electronic devices.
ABSTRACT
Transparent zinc tin oxide thin-film transistors (ZTO-TFTs) [Zn:Sn = 4:1-2:1] have been fabricated so as to estimate the electrical instability under constant current stress. The relative intensity of the drain current noise power spectra density has been shown to have a typical 1/f-noise character, and it is implied that the mobility fluctuation in ZTO-TFT [Zn:Sn = 4:1] can be enhanced by a short-range ordering in amorphous Zn-Sn-oxide, causing a larger shift of the threshold voltage (deltaV(th)).
ABSTRACT
This paper reports on the structural and optical properties of ZnCuO thin films that were prepared by co-sputtering for the application of p-type-channel transparent thin-film transistors (TFTs). Pure ceramic ZnO and metal Cu targets were prepared for the co-sputtering of the ZnCuO thin films. The effects of the Cu concentration on the structural, optical, and electrical properties of the ZnCuO films were investigated after their heat treatment. It was observed from the XRD measurements that the ZnCuO films with a Cu concentration of 7% had ZnO(002), Cu2O(111), and Cu2O(200) planes. The 7% Cu-doped ZnO films also showed a band-gap energy of approximately 2.05 eV, an average transmittance of approximately 62%, and a p-type carrier density of approximately 1.33 x 10(19) cm-3 at room temperature. The bottom-gated TFTs that were fabricated with the ZnCuO thin film as a p-type channel exhibited an on-off ratio of approximately 6. These results indicate the possibility of applying ZnCuO thin films with variable band-gap energies to ZnO-based optoelectronic devices.
ABSTRACT
A novel hybrid device structure for efficient white organic light emitting diodes has been developed, which has a high hole injection barrier between a fluorescence blue emission layer and a electron transporting layer, and therefore excitons could be confined in the emission layer close to the electron transporting layer. A phosphorescent red dopant has been introduced into the electron transporting layer to harvest triplet states of the fluorescent blue emission layer and we have succeeded in obtaining the balanced white emission from blue singlet excitons and red triplet excitons with high efficiency. The optimized device showed the maximum external quantum efficiency of about 25% at 100 cd/m2.
