Epitaxial growth of InN on c-plane sapphire by pulsed laser deposition with r.f. nitrogen radical source

We have grown InN films on c-plane sapphire substrates by pulsed laser deposition (PLD) with a radio frequency nitrogen radical source for the first time and investigated the effect of the substrate surface nitridation on the structural and electrical properties of InN films with reflection high energy electron diffraction (RHEED), atomic force microscope, the Hall effect measurements and high-resolution X-ray diffraction (HRXRD). RHEED and HRXRD characterizations revealed that high-quality InN grows epitaxially on sapphire by PLD and its epitaxial relationship is InN (0 0 0 1)∣∣sapphire (0 0 0 1) and InN [2 -1 -1 0]∣∣sapphire [1 0 -1 0]. The InN crystalline quality and the electron mobility are improved by the substrate nitridation process. The area of the pits at the InN surface is reduced by the substrate nitridation process probably due to the reduction in the interface energy between InN and the substrate. The full width at half maximum of the -1 -1 2 4 X-ray rocking curve for InN grown by the present technique without using any buffer layers was as small as 34.8 arcmin. These results indicate that the present technique is promising for the growth of the high-quality InN films.     

UV Raman spectroscopic probing into nitrogen-doped hydrogenated amorphous carbon

From the viewpoint of hardness, chemical bonding states of nitrogen-doped hydrogenated amorphous carbon film were characterized by Ultra violet (UV) Raman spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. UV Raman spectra revealed that disorder of the structure in nitrogen-doped hydrogenated amorphous carbon was promoted by applying higher bias voltages in the preparation. FT-IR spectra showed that NH bonds decreased and sp³Csp³N bonds increased with the increase of the bias voltages. The content of sp³Csp³N bonds was maximized at the bias voltage of −800 V. We found out a guarantee that the content of sp³Csp³N bonds against bias voltages correlated with the hardness obtained by nanoindentation test. The structural disorder and the increase of sp³Csp³N bonds are possible source of the hardness in the case of nitrogen-doped hydrogenated amorphous carbon.     

Parametric absolute stability of Lur'e systems

The concept of parametric stability is extended to include Lur'e-type nonlinear control systems with uncertain parameters and constant reference inputs. Conditions for parametric absolute stability are derived, which guarantee that the system remains stable despite uncertainty of equilibrium location caused by parametric uncertainties and values of the reference input. The conditions can be tested by computing value sets using the polygon interval arithmetic algorithm     

通过与热塑性树脂共热处理来改造活性炭的孔结构研究

三种具有不同比表面积的活性炭—椰壳基AC—C、粒状AC—P和竹基AC—B分别与四种热塑性前驱体（改性剂）—聚乙烯醇（PVA），羟基丙基纤维素（HPC），柠檬酸（CiA），含氟聚酰亚氨（FPI）混合后，在900℃热处理1h。通过氮气吸附法和扫描电镜对改性后活性炭的孔结构进行了表征。实验发现，热塑性树脂对活性炭AC—B的孔结构改性最显著；而另外三种改性剂PVA，HPC和CiA的改性结果使得AC—B的表面积降低，这是由于对其微孔结构改性效果不同所引起的：PVA可消除所有微孔，HPC可以有效消除极微孔，而CiA仅减少极微孔体积，但增加了超微孔体积。一方面，30％CiA的添加量，导致AC-B的外表面积增加了170％；另一方面，改性剂FPI通过增加极微孔，使其表面积增加达2倍之多。通过选择改性剂，能够改变活性炭基体中的微孔孔径分布，实际上是通过增加或减少其中的极微孔来实现。     

Energy levels and degeneracy ratios for chromium in silicon

The energy levels and the degeneracy ratios for chromium in silicon have been determined by the Hall coefficients which were measured by the van der Pauw method. Using the curve fitting method for carrier concentration based on the charge balance equation with the root mean square deviation, the analysis shows that chromium in silicon gives rise to two donor levels. The energy levels of the upper and lower donors are located at E_c-0.226(±0.010)eV and E_v+0.128(±0.005)eV, and their degeneracy ratios are 1/3 and 1/4, respectivel     

"GT target", A new high rate sputtering target of magnetic materials

A new type of a magnetic material target for high rate sputtering, "Gap Type target (GT target)" have been developed. GT target have many narrow gaps crossing the magnetic flux produced by permanent magnets attached to the cathode. Therefore, the magnetic flux being necessary for magnetron sputtering leaks out over the target surface without magnetic saturation of target materials. By using the GT target, the high rate sputtering of magnetic materials is possible even with common permanent magnets. For example, with a Fe target of 20 mm thick, the deposition rate of 1.5 μm/min. with 15 W/cm²power density is obtained by DC magnetron sputtering at argon pressure of10^{-2} sim 1.0pa.     

Microsampling technique for EBSP inspection on the cross-sections of copper trench lines in ULSIs

The crystal microstructure of copper interconnects in ultra large scale integrations (ULSIs), depends on factors such as the trench line width and patterns. Therefore, inner crystal characterisation of the desired trench lines composed of copper is required. Electron backscatter diffraction pattern (EBSP) inspection has become a powerful technique for analysing the crystal characterisation of interconnects. However, EBSP inspection is sensitive to surface conditions such as contamination and strain. In this study, we applied the focused ion beam (FIB) technology, particularly, the microsampling technique to the preparation of samples for EBSP inspection on the cross-sections of the copper trench lines. As a result, we demonstrate that a damaged layer composed of a crystalline substance is formed on the plane of the copper as revealed by the 30 kV Ga(+) FIB milling, but an EBSP signal is detectable. In conclusion, the cross-sectional sample preparation technique employing microsampling is found to be very powerful for analysing the inner crystal characteristics of the desired copper trench lines by EBSP inspection.