Polarization modulation of nanotrenches in GaN (0001)/(0001ˉ)(000\bar{1}) by surface hydrogenation

Using first-principles total-energy calculations within the framework of the density functional theory, we show that nanometer-scale trenches excavated in GaN with (0001) and $(000\bar{1})$ surfaces cause a variable electrostatic potential difference, which is tunable by controlling the hydrogen coverage of the surfaces. A positive potential difference of 3.53 V is induced between clean (0001) and $(000\bar{1})$ surfaces in nanotrenches, while a negative potential difference of −5.93 V is induced in nanotrenches with fully hydrogenated surfaces. The value of the potential difference strongly depends on the H coverage of the surfaces. Nanotrenches excavated in GaN with polar surfaces can supply electricity for various nanoscale devices consisting of molecules, clusters, and atoms inserted into the trenches

Spectroscopic Observation of the Interface States at the SiO₂/4H-SiC(0001) Interface

We obtained the energy distribution of the interface states at the SiO2/4H-SiC(0001) interface using operando hard x-ray photoelectron spectroscopy. Two types of interface states were observed: one with continuous interface states in the entire SiC band-gap and the other with sharp interface states formed below the conduction band minimum (CBM). The continuous interface states in the whole gap were attributed to carbon clusters while the sharp interface states observed near the CBM were due to the Si2—C=O state and/or the Si2—C=C—Si2 state at the SiO2/SiC interface

Growth and structural characterization of molecular superlattice of quaterrylene and N,N′-dioctyl-3,4,9,10-perylenedicarboximide

A molecular superlattice consisting of alternate layers of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) and quaterrylene was prepared by using an ultra-slow deposition technique. Film growth under equilibrium conditions with precise optimization of the substrate temperature enabled the layer-by-layer stacking of hetero-molecules at a single-layer level. The morphology of the films and the orientation of the molecules in each layer were analyzed by atomic force microscopy (AFM) and an X-ray reflection (XRR) technique

A Numerical Formula for General Prediction of Interface Bonding between Alumina and Aluminum-Containing Alloys

Interface termination between alumina and aluminum-containing alloys is discussed from a viewpoint of thermodynamics by extending the authors’ previous discussion on the interface termination between alumina and pure metal. A numerical formula to predict interface bonding at alumina-aluminum-containing alloys is proposed. The effectiveness of the formula is examined by extracting information on interface termination from experimental results and first-principle calculations in references. It is revealed that the prediction by the formula agrees quite well with the results reported in the references. According to the formula, a terminating species can be switched from oxygen to aluminum, which had been actually demonstrated experimentally. The formula uses only basic quantities of pure elements and the formation enthalpy of oxides. Therefore it can be applied for most of aluminum-containing alloys in the periodic table and is useful for material screening in developing interfaces with particular functions