Articles you may be interested inComplete band offset characterization of the HfO 2 / SiO 2 / Si stack using charge corrected x-ray photoelectron spectroscopy Structural and electronic properties of boron nitride thin films containing siliconAlthough an increasing volume of x-ray photoemission spectroscopic ͑XPS͒ data has been accumulated on boron and boron-rich compounds because of their unusual properties, including a unique three-center, two-electron bonding configuration, their common nonmetallic nature has been overlooked. Typically, the measured energy-state data are not clarified by surface Fermi level positions of these nonmetallic samples, which compromises the scientific contents of the data. In the present study, we revisited the XPS studies of sputter-cleaned ␤-rhombohedral boron (␤ r -B), the oxidized surface of ␤ r -B, B 6 O pellet, and polished B 2 O 3 , to illustrate the impact and resolution of this scientific issue. These samples were chosen because ␤ r -B is the most thermodynamically stable polytype of pure boron, B 2 O 3 is its fully oxidized form, and B 6 O is the best known superhard family member of boron-rich compounds. From our XPS measurements, including those from a sputter-cleaned gold as a metal reference, we deduced that our ␤ r -B had a surface Fermi level located at 0.7Ϯ0.1 eV from its valence-band maximum ͑VBM͒ ͑referred as E FL ) and a binding energy for its B 1s core level at 187.2 eV from VBM (E b,VBM ). The latter attribute, unlike typical XPS binding energy data that are referenced to a sample-dependent Fermi level (E b,FL ), is immune from any uncertainties and variations arising from sample doping and surface charging. For bulk B 2 O 3 , we found an E b,VBM for its B 1s core level at 190.5 eV and an E b,FL at 193.6 eV. For our ␤ r -B subjected to a surface oxidation treatment, an overlayer structure of ϳ1.2 nm B 2 O 3 / ϳ2 nm B 2 O/B was found. By comparing the data from this sample and those from ␤ r -B and bulk B 2 O 3 , we infer that the oxide overlayer carried some negative fixed charge and this induced on the semiconducting ␤ r -B sample an upward surface band bending of ϳ0.6 eV. As for our B 6 O sample, we found an E FL of ϳ1.7 eV and two different chemical states having E b,VBM of 185.4 and 187.2 eV, with the former belonging to boron with no oxygen neighbor and the latter to boron with an oxygen neighbor. The methodology in this work is universally applicable to all nonmetallic samples.

The palladium nanoparticle (Pd NP)-decorated LaAlO3 /SrTiO3 (LAO/STO) heterostructure is for the first time used as a hydrogen-gas sensor with very high sensitivity and workability at room temperature. The outstanding gas-sensing properties are due to the Pd NPs' catalytic effect to different gases, resulting in charge coupling between the gas molecules and the two-dimensional electron gas (2DEG) through the Pd NPs by either a direct charge exchange or a change of the electron affinity. These results provide insight into the emerging properties at LAO/STO interfaces.

Carbon nitride (CNx) films were prepared by reactive pulsed laser deposition at nitrogen partial pressure PN2varying from 0 to 300 mTorr. It is found that the atomic fraction of nitrogen f in the films first increases with increasing PN2, reaches a maximum of 0.32 at PN2=100 mTorr, and then decreases to a saturated value of 0.26 at PN2≳200 mTorr. Because of the absence of energetic particles in reactive pulsed laser deposition, the limited nitrogen content cannot be attributed to preferential sputtering of nitrogen that is generally observed in particle-assisted deposition of CNx films. Infrared absorption experiments show the existence of C≡N bonds and graphitic sp2 bonds. The sp2 bonds become IR active because of symmetry breaking of graphitic rings as a consequence of nitrogen incorporation. CNx films deposited at low PN2 (e.g., 5 mTorr) are more graphitic than the diamondlike pure carbon sample deposited at PN2=0, so have a slightly narrower electron band gap Eopt and a significantly higher room-temperature electrical conductivity σR. At PN2≳200 mTorr, nitrogenation of the films is very pronounced, leading to a wide band gap (Eopt≳1.5 eV), long electron band tail (E0≳0.7 eV), and extremely low σR(<1×10−13 Ω−1 cm−1). In addition, both the hardness and Young’s modulus are greatly reduced, for example, from 41.3 and 285 GPa for the pure carbon sample to 1.2 and 23.8 GPa, respectively, at f=0.32.

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Double-layered ZnO/silicon nitride microbridges were fabricated for microbridge tests. In a test, a load was applied to the center of the microbridge specimen by using a microwedge tip, where the displacement was recorded as a function of load until the specimen broke. The silicon nitride layer in the structure served to enhance the robustness of the specimen. By fitting the data to a theory, the elastic modulus, residual stress, and tensile strength of the ZnO film were found to be 137 ± 18 GPa, −0.041 ± 0.02 GPa, and 0.412 ± 0.05 GPa, respectively. The analysis required the elastic modulus, internal stress, and tensile strength of the silicon nitride layer. They were measured separately by microbridge tests on single-layered silicon nitride microbridges. The measured tensile strength of the ZnO films represents the maximum tolerable tensile stress that the films can sustain when they are used as the functional component in devices.