We find that O-vacancy (VO) acts as a hole trap and plays a role in negative bias illumination stress instability in amorphous In–Ga–Zn–O thin film transistors. Photoexcited holes drift toward the channel/dielectric interface due to small potential barriers and can be captured by VO in the dielectrics. While some of VO+2 defects are very stable at room temperature, their original deep states are recovered via electron capture upon annealing. We also find that VO+2 can diffuse in amorphous phase, inducing hole accumulation near the interface under negative gate bias.

Improving the wetting ability of Ag on chemically heterogeneous oxides is technically important to fabricate ultrathin, continuous films that would facilitate the minimization of optical and electrical losses to develop qualified transparent Ag film electrodes in the state-of-the-art optoelectronic devices. This goal has yet to be attained, however, because conventional techniques to improve wetting of Ag based on heterogeneous metallic wetting layers are restricted by serious optical losses from wetting layers. Herein, we report on a simple and effective technique based on the partial oxidation of Ag nanoclusters in the early stages of Ag growth. This promotes the rapid evolution of the subsequently deposited pure Ag into a completely continuous layer on the ZnO substrate, as verified by experimental and numerical evidence. The improvement in the Ag wetting ability allows the development of a highly transparent, ultrathin (6 nm) Ag continuous film, exhibiting an average optical transmittance of 94% in the spectral range 400-800 nm and a sheet resistance of 12.5 Ω sq, which would be well-suited for application to an efficient front window electrode for flexible solar cell devices fabricated on polymer substrates.

No abstract

Pt thin films, using the Pt precursor, dimethyl­(N,N-dimethyl-3-butene-1-amine-N)­platinum (DDAP, C8H19NPt), were deposited by atomic layer deposition (ALD). The growth characteristics of the Pt thin films were systemically investigated. A saturated growth rate was obtained with an increase in precursor and reactant pulse times, revealing the nature of the ALD self-limiting process. The growth rate increased with increasing deposition temperature and finally became saturated above 280 °C, showing a high growth rate of 0.85 Å/cycle. The short incubation time for Pt nucleation promoted the growth characteristics, which can be favorable for catalytic applications. The high reactivity and small adsorbate size produced the relatively high growth rate of the Pt thin films deposited with the DDAP precursor. A very low resistivity, close to the value of bulk Pt, was obtained for all Pt thin films deposited at various temperatures. The low resistivity was due to the similar crystalline structure and very high purity of the Pt thin films at all deposition temperatures explored in this study. In addition, Pt thin films were also deposited on a high-aspect-ratio substrate and showed good uniformity and step coverage, with a constant work function, which can be promising for electrode applications. Synthesis of Pt films by ALD using the DDAP Pt precursor and O2 is a noteworthy approach for obtaining films with a high growth rate and low resistivity.

We perform quasiparticle energy calculations to study the charge-transition levels of oxygen vacancy (VO) in HfO2. The negative-U property of VO can explain flat band voltage shifts and threshold voltage (Vth) instability in hafnium based devices. In p+ Si gate electrode, the Fermi level pinning varies by up to 0.55 eV, in good agreement with the measured values. Depending on gate bias, VO traps electrons or holes from the Si channel, causing the Vth instability. It is suggested that short time-scale charge trapping/detrapping is due to metastable VO−1 centers, whereas stable VO−2 centers dominate long time-scale instability.

No abstract

No abstract

N-Surfactant-facilitated sputter deposition provides strong selectivity for crystalline orientation and facets due to drastic decreases in the surface free energies of Ag nanoparticles supported on oxide substrates.