Showing papers on "Amorphous silicon published in 1973"

Raman Spectrum of Wurtzite Silicon

Abstract: The Raman spectrum of a metastable polycrystalline sample of wurtzite silicon is reported. The data are analyzed using a large-zone comparison with the diamond cubic phase of silicon and in terms of a simple force-constant model. These measurements are compared with the Raman spectrum of amorphous silicon and with the microcrystallite model of the amorphous phase.

Alloying of thin palladium films with single crystal and amorphous silicon

Abstract: Alpha-particle backscattering techniques have been used to investigate interdiffusion and compound formation of thin palladium films on crystalline and amorphous layers of silicon. The amorphous layers were produced by 80 keV ion implantation of 2 × 1015 cm−2 phosphorus ions. No detectable reaction between the palladium and silicon was observed after a 90 °C vacuum anneal. The compound Pd2Si, however, formed readily at 200 °C on both crystalline and amorphous silicon, and in each case preferred orientation of the Pd2Si layer was revealed by the channeling effect method. Further vacuum annealing to 310 °C showed only minor changes with no recrystallization of the ion implanted amorphous region. Mittels α-Strahlenruckwartsstreuung wurde die Interdiffusion und die Verbindungsbildung an dunnen Palladiumschichten auf kristallinen und amorphen Siliziumschichten untersucht. Die amorphen Schichten wurden durch Implantation mit 2 × 1015 cm−2 Phosphorionen von 80 keV erzeugt. Nach einer 90 °C-Vakuumtemperung wurde keine nachweisbare Reaktion zwischen Palladium und Silizium beobachtet. Die Verbindung Pd2Si bildet sich jedoch bei 200 °C schnell sowohl auf kristallinem und amorphem Silizium; in jedem Falle wurde die bevorzugte Orientierung der Pd2Si-Schicht durch den Channelingeffekt gefunden. Weitere Vakuumtemperung bei 310 °C zeigte nur geringe Anderungen ohne Rekristallisation des ionenimplantierten amorphen Bereichs.

Specific energy loss of 4He ions in silicon (amorphous, polycrystalline, and single crystal)

Abstract: The specific energy loss of 4He ions in silicon has been determined in the energy range 420–2750 keV. Several different methods of determining the specific energy loss were used to check the results. Studies were made of the variation of specific energy loss with silicon density and showed that lower‐density amorphous silicon has relatively higher specific energy losses. Studies were also made of the specific energy loss of 4He ions in radiation‐damaged silicon, polycrystalline silicon, and single‐crystal silicon. The values were then used in a thick‐target calculation to generate spectra of 4He backscattering from silicon targets. These calculations were compared to experimental spectra over a range of energies and backscattering angles. All calculations were within 2% of the experimental spectra. The ``random'' spectrum from a spinning crystal target was compared to thick‐target calculations and shown to be useful as a normalizing spectrum with an accuracy of ±5%.

Impurity effects on the structure of amorphous silicon and germanium prepared in various ways

Abstract: Thin film transmission electron diffraction patterns from amorphous silicon, prepared by ion-implantation, RF sputtering and vapour deposition (evaporation) are strikingly similar in most details except in the excact position of the diffuse peaks. For high purity silicon, either evaporated or ion-implanted, the first diffuse ring, for example, occurs consistently at a value of s(= 4π sin θ/λ) slightly lower than that of the (111) Bragg peak of the crystallized film. For sputtered films this diffuse ring appears at a higher angle than the (111) peak both in thin film electron diffraction and in x-ray scattering from thick films. The reversal is attributed to impurities, most probably oxygen or nitrogen. An analysis shows that the position of the diffuse peak in question can be correlated with the separation of second nearest-neighbours which is therefore deduced to be contracted in the impure samples. No changes in the diffraction pattern were observed on annealing, although the optical absorption...

Crystal Growth of Silicon and Germanium in Metal Films

Abstract: Amorphous silicon in contact with silver films and amorphous germanium in contact with aluminum films form crystalline precipitates when heated to temperatures well below those at which any liquid phase is present. Crystallization occurs by an initial dissolution of the semiconductor into the metal filmsolvent followed by the growth of crystals out of the solvent.

Model correction for the formation of amorphous silicon by ion implantation

Abstract: The critical dose at which an implanted amorphous layer in silicon is formed cannot be explained by a previous energy independent model. An energy dependent correction to this model can explain our ESR data as well as other data. The correction is most important for light ions.

One-band density of states for the Polk model for amorphous tetrahedrally bonded semiconductors

Abstract: The one-band density of states for the Polk model for amorphous semiconductors is found by direct diagonalization for a 201-atom structure and some smaller structures. It is seen that the density of states has a definite two-peaked character. Implications for the lower half of the valence band and the middle portion of the vibrational density of states in amorphous silicon and germanium are discussed.

Experimental Analysis of Concentration Profiles of Boron Implanted in Silicon

Abstract: The concentration profiles of boron implantations in silicon are measured using secondary ion mass spectrometry. In this method the implanted silicon is sputtered by bombardment with 5.5 keV oxygen ions. The resulting secondary B+-current is measured continuously as a function of time. The time scale is transformed into a depth scale by measuring the erosion rate. The reliability of this method is checked and discussed. This method is used in the study of the specific shape of the profiles of boron implanted in a dense crystal direction. This was done by varying the implantation conditions such as temperature, crystal direction, crystal perfection. The boron profiles in amorphous silicon were compared with theory. Another aspect studied is the profile distortion due to heat treatments. By comparison of the boron profiles with corresponding electrical profiles valuable additional information was obtained.

Process of making hollow bodies or tubes of semi-conducting materials

Abstract: Process for making semi-conducting hollow bodies by thermal splitting of volatile semi-conducting silicon compounds comprising passing the volatile silicon compounds over a carbon mold or a carbon-coated mold, and depositing thereon in three successive stages, SiO2, amorphous silicon, and polycrystalline silicon by adjustment of the temperature in each stage, and, after cooling, lifting the polycrystalline silicon body off the mold. The invention also comprises the polycrystalline Si body so made.

A possible model of amorphous silicon and germanium

Abstract: A structural model is proposed with regions consisting of identical two-dimensionally perfect layers, stacked randomly on top of one another such that bonds in adjacent layers are in either diamond-like (staggered) or wurtzite-like (eclipsed) configurations. The model has perfect tetrahedral coordination everywhere throughout such regions and is consistent with electron microscopy results and with the observed diffraction data, especially those features corresponding to the diamond (1,1,1) and (2,2,0), (3,1,1) peaks.

Energy Dependence and Annealing Behaviour of Boron Range Distributions in Silicon

Abstract: Range distributions of 10 to 250 keV boron ions implanted into amorphous (predamaged) silicon have been determined using a recently developed secondary ion mass spectrometry technique. Due to the high experimental accuracy not only characteristic distribution parameters but also variations in the profile shape could be determined. Above about 40 keV deviations from Gaussian distributions were observed as a result of increasing electronic stopping.

Amorphous silicon-electrolyte interface

Abstract: Amorphous silicon-electrolyte (AS-E) interface has been studied to determine the density of localized states in evaporated amorphous silicon films. Due to the large density of such states in amorphous semiconductors, very large fields are required to cause changes in the space-charge layer. AS-E system presents a more convenient system to meet this need for large fields than the usual MOS structure. A study of cpacitance as a function of bias shows that the density of localized states around E F is of the order of 10 18 /cm 3 · eV and that it is fairly uniform in the midgap region.

Circular etch pits in ion‐implanted amorphous silicon films

Abstract: Using a dilute HF solution as the etchant, we found very different etching behaviors between amorphous silicon films prepared by vapor deposition and by ion implantation. The latter are etched preferentially forming circular pits on the surface, but not the former. However, when the evaporated films were subjected to high dosages of ion bombardment and followed by etching, the same kind of circular pits were observed. We conclude that the bombardment of ions can cause weak spots on the amorphous Si surface which possess low resistance to the etching.

Photovoltaic effect in amorphous‐silicon‐electrolyte interface

Abstract: By studying the photovoltage developed across the amorphous silicon‐electrolyte interface on illumination with monochromatic light, the mobility gap in amorphous silicon is found to be about 1.7 eV. The effect of preparation conditions is very significant, with unannealed films deposited by electron beam evaporation showing considerable structure in the spectral response. After low‐temperature annealing, typically at 120°C for 20 h, the spectral response shows a sharp edge and is similar to that of single‐crystal silicon but is displaced to higher energies by about 0.6 eV. Sputtered films, even when unannealed, show almost identical spectral response as fully annealed films, which is attributed to the process of film growth in the sputtering process.