RESUMO
This study examined the effects of the oxygen partial pressure on the properties of tin oxide (SnOx) thin films deposited by radio frequency magnetron sputtering using a SnO target. The properties of the samples were characterized by Hall Effect measurements, dynamic-secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and atomic force microscopy. All the samples exhibited dominant Sn2+ XPS peaks, indicating that SnO with p-type conductivity was the main composition regardless of the oxygen partial pressure. The samples deposited with an oxygen partial pressure of 12% showed the best p-type characteristics, which included a maximum hole mobility of 1.94 cm²/Vs, carrier concentration of 3.83×1017/cm³, Sn2+ peak area percentage of 91.34%, Sn4+ peak area percentage of 2.35%, and Sn0 peak area percentage of 6.31%. As the oxygen partial pressure was increased to more than 12%, the Sn2+ peak area percentage decreased while the Sn4+ peak area percentage increased. This was attributed to the reduction of the SnO phase and the growth of the SnO2 phase in the samples due to the incorporation of more oxygen. These results are expected to contribute to the development of p-type SnO-based TFTs with good performance.
RESUMO
This study examined the effects of the plasma treatment of CF4 or SF6 on the properties of tin oxide (SnOx) thin films prepared at room temperature using a radio frequency sputtering technique. The properties of the samples were characterized by dynamic-secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Hall Effect measurements. All untreated samples showed Sn4+ and Sn2+ XPS peak area percentages of 57.6 and 34.6%, respectively, indicating a larger amount of SnO2 phase in the samples than SnO. The samples treated with CF4 plasma exhibited the maximum and minimum Sn4+ and Sn2+ peak areas, respectively, at a treatment time of 35 s. This was attributed to the maximum oxygen atomic percentage at 35 s and the injection of additional carbon and fluorine into the sample with increasing treatment time. On the other hand, in the case of samples treated with SF6 plasma, the Sn4+ peak area increased with increasing treatment time while the Sn2+ peak area decreased. This suggests that SnO2 is a stronger phase for samples treated with SF6 plasma for a longer duration. Furthermore, the changes in the Sn4+ and Sn2+ peak areas of the samples treated with CF4 plasma were much larger than those of the samples treated with SF6 plasma, which indicates that CF4 plasma has a larger impact on the properties of the samples. This difference in impact showed a correlation with the sharper decrease in the number of oxygen vacancies for CF4 plasma-treated samples. These results were attributed to the introduction of additional fluorine and carbon into CF4 plasma-treated samples compared to the SF6 plasma-treated ones. In addition, XRD showed that the plasma treatment did not affect the amorphous phase in the samples.
RESUMO
Solution-processed gate dielectrics were fabricated with the combined ZrO2 and Al2O3 (ZAO) in the form of mixed and stacked types for oxide thin film transistors (TFTs). ZAO thin films prepared with double coatings for solid gate dielectrics were characterized by analytical tools. For the first time, the capacitance of the oxide semiconductor was extracted from the capacitance-voltage properties of the zinc-tin oxide (ZTO) TFTs with the combined ZAO dielectrics by using the proposed metal-insulator-semiconductor (MIS) structure model. The capacitance evolution of the semiconductor from the TFT model structure described well the threshold voltage shift observed in the ZTO TFT with the ZAO (1:2) gate dielectric. The electrical properties of the ZTO TFT with a ZAO (1:2) gate dielectric showed low voltage driving with a field effect mobility of 37.01 cm(2)/Vs, a threshold voltage of 2.00 V, an on-to-off current ratio of 1.46 × 10(5), and a subthreshold slope of 0.10 V/dec.