Junjun Jia

The shift of the Fermi level in polycrystalline aluminum doped zinc oxide (AZO) films was studied by investigating the carrier density dependence of the optical band gap and work function. The optical band gap showed a positive linear relationship with the two-thirds power of carrier density ne2/3. The work function ranged from 4.56 to 4.73 eV and showed a negative linear relationship with ne2/3. These two phenomena are well explained on the basis of Burstein-Moss effect by considering the nonpa

Photon-excited B K fluorescence spectra were measured for hexagonal boron nitride using tunable synchrotron radiation below and above the B K edge. We report Raman-like resonant inelastic scattering of soft x rays involving excitation of delocalized valence-band electrons. The inelastic scattering features track with the excitation energy below threshold, go through a resonance as the excitation is tuned to the B(1s) core-exciton energy, and evolve into incoherent fluorescence as the excitation

In this study, we focused on the origin on the selective deposition of rutile and anatase TiO2 thin films during the sputtering process. The observation on microstructural evolution of the TiO2 films by transmission electron microscopy revealed the coexistence of rutile and anatase TiO2 phases in the initial stage under the preferential growth conditions for the anatase TiO2; the observations further revealed that the anatase phase gradually dominated the crystal structure with increasing film t

Amorphous indium gallium zinc oxide ($a$-IGZO) has drawn considerable interest as a channel material in flexible thin-film transistors (TFTs), to replace amorphous-Si-based TFTs, but $a$-IGZO-based TFTs show environment-dependent instability in threshold voltage. Investigating the variation of defect structures and subgap states with post-annealing temperature, this study reveals that the excess oxygen atoms surrounding cations or cation-vacancy-related defect clusters give rise to the instabili

The origin of negative ions in the dc magnetron sputtering process using a ceramic indium-gallium-zinc oxide target has been investigated by in situ analyses. The observed negative ions are mainly O− with energies corresponding to the target voltage, which originates from the target and barely from the reactive gas (O2). Dissociation of ZnO−, GaO−, ZnO2−, and GaO2− radicals also contributes to the total negative ion flux. Furthermore, we find that some sputtering parameters, such as the type of

We observed the carrier transport phenomena in polycrystalline Al-doped ZnO (AZO) films with carrier densities ranging from 2.0 × 1019 to 1.1 × 1021 cm−3. A comparison of the optical carrier density and Hall carrier density indicates that the conduction band in AZO films is nonparabolic above 2.0 × 1020 cm−3. A transition from grain boundary scattering to ionized impurity scattering is observed at a doping level of ∼4.0 × 1020 cm−3. The trap density at the grain boundary increases with increasin

This work presents the spatial distribution of electrical characteristics of amorphous indium-tin-zinc oxide film (a-ITZO), and how they depend on the magnetron sputtering conditions using O2, H2O, and N2O as the reactive gases. Experimental results show that the electrical properties of the N2O incorporated a-ITZO film has a weak dependence on the deposition location, which cannot be explained by the bombardment effect of high energy particles, and may be attributed to the difference in the spa

We investigated the dependence of valence- and core-level photoemission spectra of amorphous In2O3–ZnO (a-IZO) films on carrier density by using hard x-ray photoemission spectroscopy (hν=8000 eV). The valence band edge distinctly shifts toward high binding energy with the increase in carrier density from 0.80 to 3.96 × 1020 cm−3, and an abrupt jump for the shift of the valence band edge from high to low binding energy occurs at a carrier density of 4.76×1020 cm−3. After considering the effect of

Sputter-deposited TiO₂ films with high visible-light photocatalytic activity were successfully realized by a hybrid TiO₂/Pt/WO₃ film structure with Pt nanoparticles uniformly distributed at the interface of the TiO₂ and WO₃ films. The TiO₂/Pt/WO₃ hybrid films enable the complete decomposition of CH₃CHO under visible-light irradiation. The water contact angle of the TiO₂/Pt/WO₃ hybrid fil

Abstract Growing technical demand for thermal management stems from the pursuit of high–efficient energy utilization and the reuse of wasted thermal energy, which necessitates the manipulation of heat flow with electronic analogs to improve device performance. Here, recent experimental progress is reviewed for thermal switching materials, aiming to achieve all–solid–state thermal switches, which are an enabling technology for solid–state thermal circuits. Moreover, the current understanding for

Understanding the crystallization mechanism of amorphous metal-oxide thin films remains of importance to avoid the deterioration of multifunctional flexible electronics. We derived the crystallization mechanism of indium-based functional amorphous oxide films by using in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. Crystallization begins with surface nucleation, especially at low annealing temperatures, and proceeds simultaneous nucleation and growth in t

Epsilon-near-zero (ENZ) materials have shown significant potential for nonlinear optical applications due to their extraordinary enhancement of optical nonlinearity. Our experiments show that poly(3,4-ethylenedioxythiophene) (PEDOT) films can be modified to boost their conductivity and exhibit ENZ wavelengths from mid-infrared to visible regimes. Degenerate optical nonlinearity coefficients of EG-modified PEDOT films with an ENZ wavelength of 1587 nm are enhanced at 1550 nm to be larger than tho

We successfully fabricated a series of SnOx films varying from SnO2 to SnO using reactive sputtering. By precisely tailoring the transition region in reactive sputtering, a continuous structural evolution from SnO2 to SnO was observed with SnO2 films showing a typical columnar structure and SnO films having a dense film structure with larger crystallites. X-ray diffraction measurement confirmed that the fabricated SnO films coexist with the minor SnO2 and Sn3O4 phases. SnO films exhibit an unint