Observation Of Si Research Articles

Observation of Si [sbnd]SiO 2 interface states within the conduction band by tunneling current spectroscopy

Si SiO 2 interface states within the conduction band of Si have been examined using Al-gate metal-oxide-semiconductor (MOS) capacitors with very thin oxide films, 2.5–3.0 nm thick, thermally oxidized in dry O 2. We have developed methods of observation and calculation on the interface states by measuring the direct tunneling current through the oxide. It has been found from this method that there exist interface states within the conduction band and that their density distribution has two sharp peaks located at 7±1 and 17±1 meV above the conduction band edge. Both the peak energies are independent of the oxidation temperature, and the total state density at the interface as-oxidized at 850°C is larger than that at 1000°C.

High-Resolution Plan View Imaging of Clean and Metal Adsorbed Si Surfaces

Surface electron microscopy either in TEM or REM mode has attracted much attention. High resolution (HR) imaging of surfaces in atomic resolution level in profile or plan view imaging mode [1,2] uses surfaces of fine particles grown on peripheries of substrates. Thin self-support films with clean surfaces are generally difficult to make. Therefore, previous observations on clean Si(111)7×7 surfaces [3,4] could resolve only basic lattice fringes of the 7×7 lattice. No details of the unit cell structure have been reported.Scanning Tunneling Microscopy (STM) could reveal details of the 7×7 structure together with electronic structures [5,6]. However, STM is difficult to use for studies of surface dynamic processes. Therefore, HR-TEM is still an important technique. In the present report, HR-TEM observations of clean and metal adsorbed Si(111)7×7 and (001)2×1 with use of a 1 MV HR-UHV-EM [1,2,7] are described. An advantage to use the 1MV electron microscope is to decrease inelastic scattering as in HR-REM observations of Si(111) surfaces [8].The specimens of Si (111) and (001) crystal with thin parts were prepared by a method described previously [9]. They were clamped in a side-entry holder used in a previous REM study [8]. Thinning to a thickness transparent to the electrons were carried out by in-situ flash heating at around 1200°C.

Observation of Si and SiC surface structures using the magnetic LEED method

We have developed a magnetic LEED (MLEED) system of the so called Tucker's type. The improvement of spot intensities at very low electron energy was made with the micro-channel plate (MCP) as an image intensifier. Using this MLEED apparatus, we have clearly observed Si(111) 7×7 and SiC(0001)1×1 patterns without shadow of the specimen, particularly at normal incidence.

Observation of Si(001) Vicinal Surfaces on RHEED

We have used reflection high‐energy electron diffraction to characterize the surface step structure of Si(001) vicinal surfaces tilted from 0.5° to 4° toward the [110] azimuth. The surface of small misorientation (0.5°, 1°) after a high‐temperature anneal was double‐domain with monolayer steps, while that of a large misorientation (4°) was single‐domain with bilayer steps. The single‐domain structure appeared for all samples during homoepitaxial growth. For surfaces tilted by 0.5° or 1°, the selective growth of the first half of a monolayer was observed which changed the surface from double‐domain with monolayer steps to single‐domain with bilayer steps.

High-Resolution Reflection Electron Microscopy of Si(111)7×7 Surfaces Using a High-Voltage Electron Microscope

High-resolution reflection electron microscope (REM) observations of Si(111)7×7 surfaces have been carried out by means of an ultra-high-vacuum 1 MV microscope. An advantage to the use the high-resolution 1 MV microscope is the reduction of resolution degradation due to chromatic aberration. When the observations are carried out along the [11̄0] direction, 2.3 nm lattice fringes of the 7×7 unit cell size are observed. When several beams are included in the objective aperture, finer fringes, i.e., three fringes and seven fringes in 2.3 nm, are observed. The fact that the former fine fringes are frequently observed instead of half-spacing fringes of the 2.3 nm fringes seems to suggest that the fringes reflect the 7×7 reconstructed structure. The latter fine fringes are the narrowest fringes with spacing of 0.33 nm so far recorded in REM. When Au is deposited to form the 5×2 adsorbate structure, fringes of the half spacing of the 5 period are recorded. This may reflect the adsorbate structure, a conclusive model of which has not been reported.

ＲＨＥＥＤによるＳｉ（１００）の２×１表面構造とその上でのＳｉエピタキシーの観察

ＲＨＥＥＤによるＳｉ（１００）の２×１表面構造とその上でのＳｉエピタキシーの観察

Anomalous surface reconstruction: Observation of Si(111) 2 x 1 on sputtered and annealed Si(111) surfaces.

The 2\ifmmode\times\else\texttimes\fi{}1 \ensuremath{\pi}-bonded chain reconstruction of cleaved Si(111) is observed on sputtered and annealed Si(111) surfaces after thermal quenching. Several terraces of 2\ifmmode\times\else\texttimes\fi{}1 comprising all three principle domains are seen in a region \ensuremath{\sim}2000\ifmmode\times\else\texttimes\fi{}700 A${\mathrm{\r{}}}^{2}$, noncontiguous with domains of 7\ifmmode\times\else\texttimes\fi{}7 reconstruction that surround the 2\ifmmode\times\else\texttimes\fi{}1 area. Phase boundaries between 2\ifmmode\times\else\texttimes\fi{}1 domains are observed both on terraces (intraterrace) and between terraces (interterrace) at double-layer step transitions. I-V characteristics acquired over the 2\ifmmode\times\else\texttimes\fi{}1 terraces show good overall agreement with previous work, but differ by 0.1--0.4 V in the energy position of features in the normalized differential conductivity. This may be due to the variability in electronic structure for typical high-resolution tunneling tips, bringing into question the use of such tips for electronic-structure analysis. The presence of this phase on an otherwise 7\ifmmode\times\else\texttimes\fi{}7 surface is interpreted in terms of thermal-stress cleavage of the sample during the quench.

Observation of Si(111) surface topography changes during Si molecular beam epitaxial growth using microprobe reflection high-energy electron diffraction

Si(111) surface topography changes during Si molecular beam epitaxial growth were observed by reflection electron microscope images using microprobe reflection high-energy electron diffraction (RHEED). When RHEED intensity oscillations were observed at low substrate temperature (350 °C), it was found that the shape of atomic steps on the substrate was preserved during the growth and the surface topographies changed repeatedly with the period of the oscillations. When almost no oscillations were observed at higher substrate temperature (500 °C), the shape of the atomic steps changed during the growth. These observations provide direct evidence that RHEED intensity oscillations occur as the result of layer-by-layer two-dimensional nucleation growth.

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

Observations of clean Si(111) and gold-deposited Si(111) surfaces have been performed using micro-probe reflection high-energy electron diffraction. It was found that many atomic steps on a Si(111) surface run in nearly the same direction, about 9° off the [1̄1̄2] direction. When gold was deposited on this surface at a substrate temperature of about 800°C, 5 × 1, diffuse √3 × √3 R30°, sharp √3 × √3 R30° structures and Au clusters appeared on the surface with continuation of the deposition. During the deposition process, it was found that one kind of Si(111) 5 × 1 Au domain grew selectively along these atomic steps and nearly covered the entire surface. A phenomenon of gold clusters moving during the deposition was also observed. These clusters all moved in nearly the same direction so as to climb the atomic steps.

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

Observation of Si(111) and gold-deposited Si(111) surfaces using micro-probe reflection high-energy electron diffraction

A new colloid technique enabling domain observations of Si--Fe sheets with coating at zero field

A new method using a wetting agent in addition to a water-based magnetic ink allows domain observations of coated Si-Fe sheets without applying a normal field. No electrical apparatus whatever is needed to produce line, spike, tree, and other patterns on conventional g.o. or HI-B sheets of arbitrary size and shape.

Observation of Surface States in the Auger Spectra of Clean and Oxygen-Chemisorbed Si(111) 7×7

The first observation of Si(111) 7\ifmmode\times\else\texttimes\fi{}7 intrinsic surface states that uses Auger electron spectroscopy as a valence band spectroscopy is reported. A global inversion method based upon the fast Fourier transform was used to self-deconvolve the Auger spectra. Subsequent oxygen chemisorption is shown to give rise to ${\mathrm{O}}_{2}$ electronic levels. Only at the beginning of the oxidation stage are the surface states completely removed.

Reply to Short Note on “Observation of Si in the Field Ion Microscope”

Reply to Short Note on “Observation of Si in the Field Ion Microscope”

Short Notes on “Observation of Si in the Field Ion Microscope"

Short Notes on “Observation of Si in the Field Ion Microscope"

Observation of Si in the Field Ion Microscope

Si ribbon was made and used as a specimen tip in the field ion microscope. It had double best image voltages. This phenomenon was interpreted as being due to the band structure of Si. The position of image spots at the two voltages did not coincide, though the cause of this difference remains to be investigated. Some results for Si are compared with those for Ge.

Ionospheric Si+and SiO+

Summary. Narcisi's observation of Si+ and SiO+ ions in a thin layer at 110 km during a Leonid meteor shower implies an interconversion of these ions. It is proposed that the process involved is an ‘equilibrium’ Si+ + O2 ⇄ SiO+ + O. This process requires an elevated O2 vibrational temperature, from 500° to 1500°K, depending on uncertainties in the SiO+ bond strength. Since SiO+ presumably has a large electron dissociative recombination, the observed Si++SiO+ abundance implies a relatively large atmospheric silicon abundance as compared with other meteor species.

Optical Second-Harmonic Generation in Reflection from Media with Inversion Symmetry

The radiation at the boundary of an isotropic or cubic medium by a polarization at $2\ensuremath{\omega}$, the amplitude of which is proportional to the product of the incident laser field at $\ensuremath{\omega}$ and a spatial derivative of this field, is examined theoretically. A complete expression for the intensity and polarization of the reflected harmonic radiation as a function of the angle of incidence and state of polarization of the incident laser beam is derived. The angular dependences are in good agreement with observations on Si, Ge, and Ag. Some additional experimental results, not previously reported, are described. The magnitude of the nonlinearity due to bound electrons in these cubic materials is related to the square of the linear susceptibility, and agrees qualitatively with observations in Si, Ge, and alkali halides. This nonlinearity has the same order of magnitude as that caused by conduction electrons in metals, which has been extensively discussed in the literature. The influence of absorbed surface layers is considered.

Band edge emission properties of CdTe

Near band edge, fluorescent emission in CdTe is described. Longitudinal optical phonon spacing between emission lines is observed at 20°K. Analogous spectra in ZnS, CdS, ZnSe, CdSe and ZnTe show this to be a general rule for II–VI compounds. Emission lines of instrumentally limited width < kT were observed in CdTe, ZnTe and ZnSe. In conjunction with similar prior observations in Si, CdS and SiC, one concludes that such narrow line emission must also be of general occurrence near the band edge in semiconducting materials. A preliminary investigation of the dependence of the CdTe spectra on impurity content and conductivity type, and of the influence of temperature on position and relative intensity of emission provides useful correlations to guide further study.