Tunnel oxide passivated carrier-selective contacts based on ultra-thin SiO2 layers

We report growth by molecular beam epitaxy and structural characterization of gallium-nucleated GaAs nanowires on silicon. The influences of growth temperature and V/III ratio are investigated and compared in the case of oxide-covered and oxide-free substrates. We demonstrate a precise positioning process for Ga-nucleated GaAs nanowires using a hole array in a dielectric layer thermally grown on silicon. Crystal quality is analyzed by high resolution transmission electron microscopy. Crystal structure evolves from pure zinc blende to pure wurtzite along a single nanowire, with a transition region.

https://iopscience.iop.org/article/10.1088/0957-4484/21/38/385602/pdf

Gold-free growth of GaAs nanowires on silicon: arrays and polytypism

This paper concerns an international research project aimed at determining the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The counting procedure was based on the measurement of the molar volume and the volume of an atom in two 1 kg crystal spheres. The novelty was the use of isotope dilution mass spectrometry as a new and very accurate method for the determination of the molar mass of enriched silicon. Because of an unexpected metallic contamination of the sphere surfaces, the relative measurement uncertainty, 3 × 10−8 NA, is larger by a factor 1.5 than that targeted. The measured value of the Avogadro constant, NA = 6.022 140 82(18) × 1023 mol−1, is the most accurate input datum for the kilogram redefinition and differs by 16 × 10−8 NA from the CODATA 2006 adjusted value. This value is midway between the NIST and NPL watt-balance values.

https://iopscience.iop.org/article/10.1088/0026-1394/48/2/S01/pdf

Counting the atoms in a 28Si crystal for a new kilogram definition

Silicon carbide (SiC) as both the most important non-oxide ceramic and promising semiconductor material grows stoichiometric SiO 2 as its native oxide. During passive oxidation, a surface transformation of SiC into silica takes place causing bulk volume and bulk mass increase. This review summarizes state-of-the-art information about the structural aspects of silicon carbide, silica, and SiC–SiO 2 interfaces and discusses physicochemical properties and kinetics of the processes involved. A special section describes the electronic properties of carbide–oxide interfaces, which are inferior compared to Si–SiO 2 interfaces, limiting the use of SiC-based electronics. In the oxidation of SiC there is a variety of parameters (e.g., porosity, presence of sintering aids, impurities, crystallographic orientation, surface treatment, and atmospheric composition) influencing the process. Therefore, the kinetics can be complex and will be discussed in detail. Nonetheless, a general linear-parabolic time-law can be foun...

Silica on Silicon Carbide

XPS analysis of nanostructured materials and biological surfaces

A study was carried out for the measurement of ultrathin SiO on (100) and (111) orientation silicon wafer in the thickness range 1.5-8 nm. XPS, medium-energy ion scattering spectrometry (MEIS), nuclear reaction analysis (NRA), RBS, elastic backscattering spectrometry (EBS), SIMS, ellipsometry, gazing-incidence x-ray reflectometry (GIXRR), neutron reflectometry and transmission electron microscopy (TEM) were used for the measurements. Water and carbonaceous contamination about 1 nm were observed by ellipsometry and adsorbed oxygen mainly from water at thickness of 0.5 nm were seen by MEIS, NRA, RBS and GIXRR. The different uncertainty of the techniques for the scaling constant were also discussed.

H Y. Chen

Papers

Critical Review of the Current Status of Thickness Measurements for Ultrathin SiO2 on Si, Part V: Results of a CCQM Pilot Study

Ultra-thin SiO2 on Si, Part V: Results of a CCQM Pilot Study of Thickness Measurements