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SnO2 thin films were deposited on quartz substrates by pulsed laser deposition and postannealed at different temperatures in oxygen ambience. X-ray diffraction, Hall measurement, and x-ray photoelectron spectroscopy were employed to investigate the properties of the annealed SnO2 thin films. An anomalous electrical transport behavior as a function of the annealing temperature was observed. Both the growth of the crystal grain and oxygen vacancy density variation in the annealing process have been identified to be responsible for the transition of electrical transport properties. [ABSTRACT FROM AUTHOR]

In this paper, the thermal stability of TiN metal gate with various composition prepared by different preparation technology [(e.g., atomic layer deposition (ALD) or physical vapor deposition (PVD)] on HfO2 high-K dielectric is investigated and compared by physical and electrical analysis. After annealing of the TiN/HfO2 stack at 1000 °C for 30 s, it is observed that: (1) Nitrogen tends to out-diffuse from TiN for all the samples; (2) Oxygen from the interfacial layer (IL) between HfO2 and Si tends to diffuse toward TiN. PVD Ti-rich TiN shows a wider oxygen distribution in the gate stack, and a thinner IL than the N-rich sample. Ti penetration into HfO2 is also observed in the Ti-rich sample, which can potentially lead to the dielectric break-down. Besides, the oxygen out-diffusion can be significantly suppressed for ALD TiN compared to the PVD TiN samples. [ABSTRACT FROM AUTHOR]

High quality HfO2 dielectrics have been grown on epitaxial graphene on 4H-SiC substrates and have been studied by using in situ x-ray photoemission spectroscopy. The in situ thermal treatment shows that the HfO2/graphene/4H-SiC heterojunctions have good thermal stability up to 650 °C. A shift of core-level spectra from graphene layer implies that charge transfer takes place at the interface. The high thermal stability and sufficient barrier heights between HfO2 and graphene indicate that high-k dielectric grown on graphene is very promising for the development of graphene-based electronic devices. [ABSTRACT FROM AUTHOR]

High quality HfO2 dielectrics have been grown on ZnO (0001) substrates. The valence- and conduction-band offsets for HfO2/ZnO (0001) heterojunctions have been determined to be 0.14±0.05 and 2.29±0.05 eV, respectively, by using in situ x-ray photoemission spectroscopy. First-principles calculations show that the valence-band offset at the HfO2/ZnO (0001) interface of the most energetically favorable interface structure is 0.40 eV, which is consistent with the experimental results. [ABSTRACT FROM AUTHOR]

We report first principles calculations on the magnetism and electronic structures for nitrogen-doped anatase TiO2 (N:TiO2). Our calculations indicate that magnetic state is the ground state for N:TiO2 systems. An isolated N atom produces a total magnetic moment of 1.00μB and introduces spin-polarized 2p states in the band gap. The origin of the magnetic moments is the holes in N 2p π band of the N dopant. Several doping configurations studied suggest the existence of ferromagnetic coupling between N dopants. The ferromagnetism in N:TiO2 can be attributed to the hole-mediated double exchange through the strong p-p interaction between N and O. [ABSTRACT FROM AUTHOR]

An epitaxial Ni thin film is grown on a LaAlO3 single-crystalline thin film on Si (001). The p-type Schottky barrier height at the Ni/LaAlO3 interface is measured to be 2.88 eV by x-ray photoemission spectroscopy. The effective work function of the Ni film on LaAlO3 is determined to be 5.15 eV. Good epitaxial quality and a high effective work function suggest that Ni is a promising gate material integrated with LaAlO3 dielectric films for p-type metal oxide semiconductor field effect transistors. [ABSTRACT FROM AUTHOR]

High quality GeO2 dielectrics were prepared on Ge(001) surface by direct atomic source oxidation. The band alignments have been studied by using high resolution x-ray photoemission spectroscopy. The valence and conduction band offsets at GeO2/Ge(001) interface are 4.59±0.03 and 0.54±0.03 eV, respectively. The calculated projected density of states indicate that the formation of germanium and oxygen vacancies at different oxidation stages might result in the reduction of valence band offsets, which clarified the varied experimental results of valence band offset [M. Perego et al., Appl. Phys. Lett. 90, 162115 (2007) and V. V. Afanas’ev and A. Stesmans, Appl. Phys. Lett. 84, 2319 (2004)]. [ABSTRACT FROM AUTHOR]

We propose an interface model for Ge and its surface passivating nitride. The β-Ge3N4(0001)/Ge(111) interface structure does not have dangling bonds and is predicted to be exceptionally stable compared with other possible structures. Band offsets determined using x-ray photoemission spectroscopy study are in agreement with the prediction by first-principles calculations. The band offsets are large enough to minimize possible carrier tunneling. [ABSTRACT FROM AUTHOR]

The band alignment and thermal stability for HfO2 films on SiC with and without nitridation have been studied by using photoemission spectroscopy. The valence- and conduction-band offsets at HfO2/4H-SiC interfaces were measured to be 1.02 and 1.53 eV, respectively. The atomic source nitridation improves interface thermal stability with nitrogen passivation for the oxygen vacancies in dielectric films and for the defects on SiC surface, but induces band gap reduction for the HfO2 dielectric layer and band alignment shift at the interface. Postnitridation annealing helps to improve the band offsets of dielectric film to have sufficient injection barrier. [ABSTRACT FROM AUTHOR]

The effect of interfacial oxynitride layer on the band alignment and thermal stability of amorphous LaAlO3/Si0.75Ge0.25 heterojunction has been investigated. The presence of interfacial oxynitride layer shifts the band alignment due to the modification of interfacial dipole. During the thermal annealing, it was found that the interfacial electronic structures were altered, and the valence-band maximum of LaAlO3 films shifted to the lower energy due to the diffusion of nitrogen species from the interfaces into LaAlO3 films at high annealing temperature. [ABSTRACT FROM AUTHOR]

The nitrogen-doping induced changes in optical properties and electronic structures of SrTiO3 films have been investigated by using spectroscopic ellipsometry and x-ray photoemission spectroscopy. Combined with the first-principles calculations, it is found that the localized N 2p states above O 2p states are attributed to the new absorption edge at 500 nm and the photoactivity in the visible light region. Our results are consistent with both recent experimental and theoretical studies on nitrogen-doped TiO2, where the visible light responses arise from the localized N 2p states slightly above the valence-band edge rather than the band gap narrowing. [ABSTRACT FROM AUTHOR]

The energy-band alignments for LaAlO3 films on p-Ge(001) with and without GeOxNy interfacial layer have been studied using photoemission spectroscopy. The valence-band offsets at LaAlO3/GeOxNy/Ge and LaAlO3/Ge interfaces were measured to be 2.70 and 3.06 eV, respectively. The effect of interfacial GeOxNy layer on the band alignments is attributed to the modification of interface dipoles. The conduction-band offsets at LaAlO3/Si(001) and LaAlO3/Ge interfaces are found to have the same value of 2.25±0.05 eV, where the shift of valence-band top accounts for the difference in the energy-band alignment at two interfaces. [ABSTRACT FROM AUTHOR]

Ge3N4 dielectrics were prepared on Ge surface by in situ direct atomic source nitridation. The thermal stability and band alignments for Ge3N4/Ge interfaces have been studied by using high-resolution x-ray photoemission spectroscopy. The in situ thermal treatment shows that Ge3N4 film has higher temperature thermal stability up to 550 °C in vacuum. The conduction- and valence-band offsets at Ge3N4/Ge interface are quite asymmetrical with the values of 2.22 and 1.11 eV, respectively. [ABSTRACT FROM AUTHOR]

The effect of nitrogen incorporation on the electronic structure and thermal stability of HfO2 gate dielectric was investigated by using photoemission study and first-principles calculation. Hafnium oxynitride (HfON) dielectric shows higher thermal stability in comparison to pure HfO2 on Si. Atomic N can passivate O vacancies in the dielectrics during nitridation process, but the N atoms incorporated into interstitial sites cause band gap reduction. Postnitridation annealing is required to activate interstitial N atoms to form stable N–Hf bonds, which will increase the band gap and band offset of as-nitrided dielectric film. [ABSTRACT FROM AUTHOR]

The annealing temperature effect on the band structure of Ba0.65Sr0.35TiO3 (BST) thin films coated on n-type Si(100) substrate was investigated by ellipsometry and x-ray photoelectron spectroscopy. The band energy shifts of sol-gel BST films annealed at different temperatures are dependent on their developed microstructure. Related to the amorphous BST films annealed at 600 °C, the polycrystalline BST film annealed at 700 °C exhibits narrow band gap, upwards-moved Fermi level, and downwards-moved conduction band minimum, which are believed to contribute the enhanced field emission of BST-coated Si field emitter arrays. [ABSTRACT FROM AUTHOR]

The reactions of yttrium (Y) metal on silicon (Si) are investigated by x-ray photoelectron spectroscopy (XPS). Low-temperature annealing studies are performed to investigate the diffusion of Si. It is found that Si diffusion occurs even under low annealing temperatures of <300 °C in an ultrahigh vacuum environment. This is attributed to the weakening of the Si–Si covalent bonds by metallic Y. XPS depth profiling of room-temperature-oxidized films revealed a possible oxygen-mediated pathway which allowed significant Si diffusion at room temperature for silicate formation. [ABSTRACT FROM AUTHOR]

Co overlayers of ∼3 nm have been deposited at room temperature on rutile TiO2 (100) surfaces, followed by annealing to different temperatures. Ferromagnetic behavior has been observed for all samples, but the saturation magnetic moment (μS) per Co atom is seen to decrease with increasing annealing temperature up to 530 °C. In situ photoemission studies show that the reduction of the saturation magnetic moment is accompanied by Co oxidation at high annealing temperature. However, an annealing temperature of 700 °C leads to an increase of the saturation magnetic moment. At this temperature, the formation of an additional Co–Ti–O ternary compound phase is observed by high-resolution transmission electron microscopy. It is proposed that this phase is responsible for the increase of the saturation magnetic moment. The origin of ferromagnetism might be the same as that of Co-doped TiO2. [ABSTRACT FROM AUTHOR]

A surface passivation method to improve the film quality of HfO2 gate dielectric on Ge substrate by using ultrathin AlNx layer is reported. Results show that the AlNx passivation layer is more effective in suppressing the GeOx formation at the HfO2/Ge interface, resulting in improved C–V characteristics, than surface nitridation-passivated Ge devices. In addition, a thermal stability study shows AlNx passivation is promising for future Ge metal–oxide–semiconductor devices. [ABSTRACT FROM AUTHOR]

Conductive oxides RuOx as alternative electrode on high-κ HfO2 gate dielectric have been fabricated by ultrahigh-vacuum sputtering and subsequently oxidized using oxygen plasma. The energy-band alignment for the RuOx/HfO2/Si system and the oxidation-state dependence of barrier height for RuOx contacting to HfO2 dielectrics has been analyzed by x-ray photoemission spectroscopy. The valence- and conduction-band offsets of HfO2/Si are determined to be 3.05±0.1 and 1.48±0.1 eV, respectively. The barrier heights for the RuOx contacting to HfO2 are oxidation-state dependent, in the range of 1.95–2.73 eV. [ABSTRACT FROM AUTHOR]

The energy-band alignments for the ZrO2/Si, ZrO2/Si0.75Ge0.25, and ZrO2/Ge interfaces have been studied using x-ray photoemission. The valence-band offsets of ZrO2/Si, ZrO2/Si0.75Ge0.25, and ZrO2/Ge interfaces are determined to be 2.95, 3.13, and 3.36 eV, respectively, while the conduction-band offsets are found to be the same value of 1.76±0.03 eV for three interfaces. The upward shift of valence-band top accounts for the difference in the energy-band alignment at three interfaces. [ABSTRACT FROM AUTHOR]

A dynamic process consisting of a series of reactions during deposition of HfO[SUB2] films on SiO[SUB2]-covered silicon under oxygen-deficient conditions is identified. The oxygen-deficient HfO[SUBx<2] layer absorbs the oxygen in the SiO[SUB2] layer to form fully oxidized metal oxide film. As a result, there) is no silicate and silicon oxide formed at the interface with silicon substrate. Thermodynamic analysis indicates that even if there is a layer of silicate forming at the initial stage of deposition, the silicate layer will be decomposed with the progress of HfO[SUBx<2] deposition. [ABSTRACT FROM AUTHOR]

The kinetics of the interfacial layer (IL) growth between Hf aluminates and the Si substrate during high-temperature rapid thermal annealing (RTA) in either N[sub 2] (∼10 Torr) or high vacuum (∼2×10[sup -5] Torr) is studied by high-resolution x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy. The significant difference of the IL growth observed between high vacuum and relatively oxygen-rich N[sub 2] annealing (both at 1000 °C) is shown to be caused by the oxygen species from the annealing ambient. Our results also show that Hf aluminates exhibit much stronger resistance to oxygen diffusion than pure HfO[sub 2] during RTA in N[sub 2] ambient, and the resistance becomes stronger with more Al incorporated into HfO[sub 2]. This observation is explained by the combined effects of (i) smaller oxygen diffusion coefficient of Al[sub 2]O[sub 3] than HfO[sub 2], and (ii) higher crystallization temperature of the Hf aluminates. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

High-resolution x-ray photoelectron spectroscopy (XPS) was applied to characterize the electronic structures for a series of high-k materials (HfO[sub 2])[sub χ] (Al[sub 2]O[sub 3])[sub 1 - χ] grown on (100) Si substrate with different HfO[sub 2] mole fraction χ. Al 2p, Hf 4ƒ, O 1 s core levels spectra, valence band spectra, and O 1 s energy loss all show continuous changes with χ in (HfO[sub 2])[sub χ](Al[sub 2]O[sub 3])[sub 1 - χ]. These data are used to estimate the energy gap (E[sub g]) for (HfO[sub 2])[sub χ](Al[sub 2]O[sub 3])[sub 1 - χ], the valence band offset (ΔE[sub v]) and the conduction band offset (ΔE[sub c]) between (HfO[sub 2])[sub χ](Al[sub 2]O[sub 3])[sub 1 - χ] and the (100) Si substrate. Our XPS results demonstrate that the values of E[sub g], ΔE[sub v], and ΔE[sub c] for (HfO[sub 2])[sub χ](Al[sub 2]O[sub 3])[sub 1 - χ] change linearly with χ. [ABSTRACT FROM AUTHOR]