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4H-SiC n-channel metal oxide semiconductor field effect transistors (NMOSFETs) with a Ba-silicate interface layer were irradiated with gamma-rays up to 850 kGy at room temperature. Above 600 kGy, the field effect mobility increased from 12 to 18 cm2 V−1 s−1. The narrower channel in the NMOSFETs enhanced radiation responses, such as mobility enhancement and threshold voltage shift. These results indicate that the edge of the channel significantly modifies the electrical characteristics.

As an extremely thin diffusion barrier applicable to Cu interconnects for the 45 nm technology nodes, we propose a barrier material without interface layers that can become a cause of barrier consumption owing to solid-phase reaction and/or intermixing. We examine the barrier properties of a reactively sputtered ZrN barrier as thin as 5 nm between Cu and SiOC. The ZrN barrier with a slightly N-rich composition tolerates annealing at 500 °C for 30 min. Transmission electron microscopy indicates the absence of interface layers adjoining the barrier. Using the ZrN barrier, we can demonstrate the effectiveness of the interface-layer-free characteristics for an extremely thin barrier of high performance.

The effects of Pd, Ni, Nb, and Ti interface layers on the thermal stability of Ag films were investigated, and those metals that are appropriate for the interface layers were summarized. The results indicated that Ti and Nb interface layers resulted in thermally stable Ag films by improving the adhesion strength of the Ag films to SiO2 substrates and by enhancing the crystal orientation of Ag(111). It was determined that appropriate interface layer metals for Ag film should have a large Gibbs free energy of formation for the oxide and an appropriate atomic diameter ratio of d metal/d Ag.

The wavelength dependence of SiN x :H/Si interface defect generation caused by vacuum ultraviolet (VUV)/UV radiation from plasma etching processes was investigated. VUV radiation (λ< 200 nm) had almost no impact on the generation of defects at the SiN x :H/Si interface, since all the radiation in this wavelength range was absorbed in the upper SiN x :H film. However, UV radiation (200 < λ< 400 nm) was able to reach the underlying SiN x :H/Si interface and damage the interface. Direct UV radiation reaching the SiN x :H/Si interface dissociated the chemical bonds at the interface and generated interface-trapped charges. The estimated total energy of absorbed photons (E total; 200 < λ< 400 nm) at the interface layer seems to be proportional to the interface-trapped charge density (D it) measured by capacitance–voltage measurement. However, the mechanism underlying the relationship between E total and D it is not yet clear. Visible radiation (λ> 400 nm) had no influence on damage generation on the SiN x :H/Si structure, since the visible radiation was transmitted through upper SiN x :H film and underlying interface layer. The results revealed that UV radiation transmitted through the upper dielectrics can cause the electrical characteristics of underlying metal–oxide–semiconductor (MOS) devices to fluctuate.

Two-dimensionally standing graphene sheets, i.e., carbon nanowalls (CNWs), were synthesized on a Si substrate employing a capacitively coupled fluorocarbon plasma-enhanced chemical vapor deposition system together with H radical injection. To apply CNWs in electronic devices and/or membrane filters, we have demonstrated the reactive ion etching (RIE) of CNWs. RIE employing H2/N2 gases showed that the CNW films were anisotropically etched at a relatively high rate of more than 250 nm/min. However, the 10-nm-thick interface layer between a CNW film and the Si substrate remained and the interface layer was not completely etched. In contrast, RIE employing Ar/H2 gases enabled us to completely remove the interface layer. Ar/H2 RIE was also carried out from the bottom surface of CNW films after exfoliating them from the Si substrate. As a result, a free-standing CNW film of 550 nm thickness without an interface layer as a membrane filter was successfully formed.

Graphene can be grown on three major low-index substrates of Si(111), (110), and (001) by forming a 3C-SiC thin film and by subliming Si atoms from the top few layers of the SiC film. We have investigated the structure of graphene/3C-SiC interface by cross-sectional transmission electron microscopy (XTEM) and Raman-scattering spectroscopy. While the interface layer quite similar to that on the graphene/6H-SiC(0001) face is found to exist on the 3C-SiC(111)/Si(111) substrate, no such interface structure exists on the (110)- and (001)-oriented faces.

A nitride layer was formed on a SiC surface by direct nitridation in NH3 or N2. The surface was characterized by X-ray photoelectron spectroscopy (XPS). The thickness of the nitride layer was estimated to be less than 2 nm. The metal–insulator–semiconductor (MIS) Schottky diode was formed on SiC using the nitride layer as the interface layer to estimate the interface state density between the nitride layer and the SiC substrate from the diode factor n. The interface state density was on the order of 1011–1012 eV-1·cm-2 at 0.3 eV below the conduction band edge. A SiO2 film was deposited on the nitridation layer to form an MIS diode. The interface state density of the SiO2/nitride/SiC sample was lower than that of the MIS Schottoky diode.

We deposited interpoly-stacked dielectric films with Si3N4/SiO2/Si (ON) and SiO2/Si3N4/Si (NO) structures by the atomic layer deposition method. The multilayer structure of these films with the interfaces was investigated by O and N K-edge X-ray absorption spectroscopy, nondestructive method. The electrical properties of the films were also estimated in comparison with those of Si3N4 and SiO2 single layers. A few defects existed in the interface layer of both NO and ON structures. In particular, the oxynitride interface layer was detected in the NO multilayer. The ON stacked structure had a lower leakage current and higher breakdown voltage than the NO structure and had very similar electrical properties to those of the SiO2 single layer.

A subnanometer thick organic molecule layer was prepared on a SiO2/Si substrate using 3-mercaptopropyltrimethoxysilane (MPTMS) possessing a thiol moiety as a feature. 60-nm-thick Ag films were deposited on SiO2/Si substrates with and without the MPTMS layer at the interface and their thermal stabilities were compared. After annealing at 400 °C, Ag thin films with the MPTMS interface layer showed better stability than those without the MPTMS interface layer, as determined from the results of morphological observation. The enhancement is considered to be caused by strong bonding between Ag atoms and the thiol moiety in MPTMS.

The oxidation mechanism at the HfO2/Si interface is discussed by investigating oxidation kinetics on the basis of experimental results that were obtained using the technique of grazing incidence X-ray reflectivity (GIXR) in combination with spectroscopic ellipsometry (SE) measurements. In a relatively thick HfO2 region, the interface layer growth shows a logarithmic dependence on annealing time, while the activation energy of oxidation is very small compared with that of conventional oxidation. These results clearly indicate that the oxidation mechanism at the HfO2/Si interface is different from that at the Si surface. Moreover, it is also reported that the oxidation at the HfO2/Si interface has no surface orientation dependence, no HfO2 thickness dependence and a slight O2 pressure dependence. All of the results obtained in this work suggest that atomic oxygen is involved in the oxidation at the HfO2/Si interface and the diffusion of oxygen atoms in the interface layer limits oxidation rate in a relatively thick HfO2 region. On the other hand, in an ultra-thin HfO2 region, HfO2 thickness dependence and Si surface orientation dependence are observed. These results suggest that both atomic oxygen and molecular oxygen are involved in the interface oxidation in an ultra-thin HfO2 region. On the basis of the results, we propose a kinetic model for the oxidation associated with both atomic oxygen and molecular oxygen at the HfO2/Si interface.

The increase in switching charge of as-grown SrBi2Ta2O9 (SBT) capacitors with polarization reversal was investigated. We call this phenomenon wake-up. The switching charge was increased and the rectangularity of the D-E hysteresis loops was improved with polarization reversal. The switching pulse with larger amplitude, longer width and shorter period generated a larger increase in the switching charge with polarization reversal. At the same time, the capacitors came to exhibit a rapid increase in leakage current at a certain applied field after the switching. Furthermore, the D-E hysteresis loop of the capacitors with wake-up shifted toward the positive- or negative-bias field according to the sweeping direction of the applied voltage. We have concluded that some spontaneous polarizations locked by localized space charges at the interface layer in the wake-up-exhibiting SBT capacitors were freed by the application of numerous switching pulses, and trap levels generated in the interface layer by the switching rendered the rapid increase in leakage current and the voltage shift of D-E hysteresis easy.

The initial stage of SiO2/Si interface formation on an atomically flat hydrogen-terminated Si(100)-2×1 surface was studied by X-ray photoelectron spectroscopy. The following results were obtained: 1) the initial stage of interface formation does not depend on the initial surface morphology, 2) the interface layer becomes continuous at the oxide film thickness of 0.5 nm, and 3) at thicknesses greater than this the deviation from an atomically flat interface increases with the progress of oxidation, however, an abrupt compositional transition occurs.

Negative-electron-affinity (NEA) GaAs/GaP photocathodes have been grown by MBE for the first time. The surfaces of GaAs emitters are atomically smooth. The compositionally graded interface layer GaAsP produced by infer-diffusion at the GaAs/GaP interface has played an important role for a high photoemissive quantum yield and for the spectral response curves of photoemission from the thin GaAs layers.

Surface and bulk defect densities in undoped a-Si:H films on a quartz substrate are estimated from the thickness dependence of the defect density by ESR and constant photocurrent method (CPM). For the first time, the thickness of a defective surface layer in a-Si:H is determined by ESR to be about 200 Å. The decrease in surface spin density by HF etching treatment and the difference in photoconductivities measured by illumination from different sides suggest that the free surface layer is more defective than the interface layer on a quartz substrate.

Junction leakage current was studied in shallow p+-n diodes formed by using BF+ 2-implantation and rapid thermal annealing (RTA). It is s hown that the bulk leakage component is 3 to 4 times larger in BF+ 2-implanted diodes than in B+-implanted diodes. Dislocations created in the BF+ 2-implanted layer during the RTA are not the direct cause of this leakage increase. It was also found that the surface leakage component is increased by the RTA. Rapid heat treatment may increase interface states and/or g-r centers in the Si/SiO2 interface layer.

In-depth profies of the oxide layers prepared by thermal, anodic and plasma oxidations were compared by means of a simultaneous measurement of AES-SIMS. In the AES measurements, it was found that oxide by thermal oxidation consisted of only Ga-oxide and big pile-up of As was grown between the oxide and the GaAs substrate. In case of the anodic and plasma oxidations, much thinner interface layer was formed than that by thermal oxidation and no pile-up of As was observed. The SIMS measurements revealed detailed structure of the interface region for the anodic and plasma oxidations and that small amount of oxygen may diffuse into the GaAs substrate during the process of plasma oxidation. The chemical compositions were estimated as Ga2O3 for the thermal, GaAsO2 for the anodic and GaAsO for the plasma oxidations, respectively.

InAsSbP-InAs superlattices were grown by organometallic vapor phase epitaxial growth. The superlattice periods were obtained by X-ray diffraction measurements. The compositional depth profiles were observed by Auger electron spectroscopy and simultaneous argon-ion sputter etching. The chemical interface layer width was measured to be less than 60 A for the superlattice with a 335 A period. The results suggest that organometallic vapor phase epitaxy is one of the most useful methods for the growth of high quality superlattices.