I. H. Wilson

The effects of self‐ion bombardment (30–500 keV) on the surface topography of single‐crystal germanium

High‐resolution scanning electron microscopy has been used to observe the effects of self‐ion bombardment on the topography of germanium surfaces. Holes (mean separation 400 A) appeared in the surface at doses above 2×1015 ions/cm2 (ion energy 50 keV). These enlarged with increasing ion dose and developed into a complex cell structure. This structure underwent no further gross change for doses above 1×1017 ions/cm2, where the mean cell diameter was ∼1200 A. The surface preparation was found to have no influence on the appearance of this cellular structure. Some specimens were fractured after bombardment to observe a section of the bombarded surface. A porous layer of thickness 2.5 times the projected range (Rp) was observed at doses just below those where changes in surface topography were first observed. At the highest dose (4×1017 ions/cm2) the thickness of this layer was 6Rp. The cellular surface structure was observed at all ion energies chosen so long as the energy deposited in the surface by the ion...

The topography of sputtered semiconductors

Abstract The surfaces of semiconductor single crystals were observed using a scanning electron microscope after bombardment at normal incidence at room temperature with doses between 0.5 × 1018 and 3 × 1018 of 40 keV argon ions/cm2. The usual topography of the sputtered surface and the perturbing effects of dirt and contamination are reported, and observations of the variation of topography with dose are reported for GaAs. An explanation for the features observed is discussed with particular reference to current models of cone formation and secondary processes such as flux enhancement at the foot of steep slopes. The behaviour of Si, Ge, GaAs and InP was consistent with an amorphous surface. In the case of CdTe, CdS and GaP it appeared that the crystal structure was retained resulting in a topography of the sputtered surface that is sensitive to orientation. InSb appears to undergo a chemical change during ion bombardment.

Heat transfer between two metallic surfaces at small distances

In scanning thermal microscopy, but also in scanning tunneling microscopy, the thermal contact between tip and sample plays an important role. The heat transfer across the vacuum gap between two parallel metallic surfaces, if the gap width is decreased below several microns, has been investigated. At these distances propagating electromagnetic modes die out but simultaneously a transfer of nonpropagating surface modes across the gap becomes more probable. The heat conductance of the vacuum gap should become distance dependent and larger than that given by the Stefan–Boltzmann law; however, the experimental results and theoretical considerations indicate that the heat transfer, based on the discussed proximity mechanism, is very small, smaller than predicted by the theory of Polder and Van Hove [Phys. Rev. B 4, 3303 (1971)].

Structure control and characterization of SrBi2Ta2O9 thin films by a modified annealing method

SrBi2Ta2O9 (SBT) ferroelectric thin films were prepared by metalorganic decomposition on Pt/Ti/SiO2/Si substrates at annealing temperatures ranging from 600 to 750 °C. The SBT thin films were annealed layer by layer during the spin-coating process using a rapid thermal annealing (RTA) furnace. The relative intensity of (200) peak in x-ray diffraction increased with the increase of the annealing temperature. A (200)-predominant film can be formed at 700 and 750 °C. For the film annealed by RTA furnace at 650 °C, the remanent polarization (2Pr) and coercive field (2Ec) were 19.8 μC/cm2 and 116 kV/cm, respectively.

Oxygen gettering and oxide degradation during annealing of Si/SiO2/Si structures

The microscopic nature of the degradation of oxide layers in Si/SiO2/Si structures induced by annealing in the temperature range 1200–1320 °C in inert or weakly oxidizing atmospheres has been studied. Electron‐spin‐resonance measurements have been performed on unannealed and annealed samples subsequently subjected to γ or X radiation or hole injection. Two oxygen‐vacancy‐related defect centers were observed, the monovacancy Eγ’ center and the multiple vacancy Eδ’—both were observed in substantially larger numbers in annealed oxides as compared to unannealed oxides. Etchback profiling of the paramagnetic defect distributions shows that they are distributed nonuniformly throughout the annealed oxides with the highest densities close to the two Si/SiO2 interfaces. Electrical measurements of fixed oxide charge induced by X irradiation indicate that annealing results in the creation of both positive and negative charge traps. The numbers of positive trapped charges and their radiation dose dependence are incon...

A model for the evolution of implanted oxygen profiles in silicon

Abstract The model described predicts the distribution of oxygen implanted in silicon, simulating the formation of a buried layer of SiO 2 . It takes into account a phase change due to the formation of SiO 2 , changes in the projected range and higher moments of the oxygen distribution, sputter etching and redistribution of oxygen. The sensitivity of the model to all the modelling parameters is demonstrated and oxygen concentrations calculated for various implanted doses are compared with experimental results obtained by Rutherford backscattering, cross-sectional transmission electron microscopy and secondary ion mass spectrometry.

Low-temperature preparation and characterization of SrBi2Ta2O9 thin films on (100)-oriented LaNiO3 electrodes

SrBi2Ta2O9 (SBT) ferroelectric thin films were prepared by the metalorganic decomposition technique at annealing temperatures of 600 and 650 °C on Pt/Ti/SiO2/Si substrates coated by (100)-oriented LaNiO3 (LNO) metal oxide thin films, which were fabricated by the sol–gel technique combined with a layer-by-layer annealing method at 600 °C. A (200)-predominant SBT thin film can be formed on LaNiO3(100)/Pt/Ti/SiO2/Si substrate at 600 °C. The effect of the LNO oxide electrode on the dielectric and ferroelectric properties of SBT thin film annealed at 600 °C was studied. Although the remanent polarization of the (200)-predominant SBT thin film is not as large as expected, the film can be uniformly polarized and imaged using an atomic force microscope in the piezoelectric mode.

Characterisation of proton irradiated Ba0.65Sr0.35TiO3/P(VDF-TrFE) ceramic- polymer composites

Abstract Barium strontium titanate/poly (vinylidene fluoride-trifluoroethylene)70/30 (Ba0.65Sr0.35TiO3/P(VDF-TrFE) 70/30) composite with high dielectric permittivity was developed by integrating high dielectric permittivity ceramic powder with proton irradiated polymer matrix. The composite after irradiation behaves as a relaxor ferroelectric material and this behaviour is similar to that of irradiated P(VDF-TrFE) 70/30 co-polymer. Due to the irradiation, dielectric peaks broadened and moved towards the lower temperature, creating high relative permittivity values in a broad temperature range. Ba0.65Sr0.35TiO3/P(VDF-TrFE) composite with 0.5 ceramic volume fraction with a dosage of 80 Mrad can reach a relative permittivity of ∼160 at room temperature (at 1 kHz), which is about 14 times higher than that of pure copolymer. Polarization-electric field hysteresis loops of composites are strongly depended on the ceramic powder volume fraction and the effects of irradiation is less apparent in composites with higher ceramic powder volume fraction.

Magnetic domain structures of Co22Ag78 granular films observed by magnetic force microscopy

A magnetic force microscope (MFM) was used to image the topography and magnetic microstructures of Co22Ag78 granular films. The observed morphology shows isolated nanometer-scale cobalt particles (granules) embedded in the silver matrix. Stripe magnetic domains with much larger size (typically of ∼100 nm wide) than that of cobalt particles are resolved clearly on MFM micrographs for the annealed samples. It is demonstrated that the domain width and the relative magnetic force strength first increases and then decreases with annealing temperature with a maximum at about 600 K. We suggest that the appearance of the stripe domains is attributed to magnetic correlation among many of the isolated single-domain cobalt particles and is dependent on the microstructure of the samples.

Rutherford backscattering analysis of oxide layers formed by ion implantation into single-crystal silicon

Abstract Single-crystal silicon was implanted with 40 keV and 60 keV oxygen ions. Rutherford backscattering (RBS) analysis was used to determine the oxygen profile, the ratio of oxygen to silicon in the implanted layer and the extent of radiation damage for doses up to 3 × 10 18 ions cm -2 . The measured oxygen profiles appear to agree with theory at low doses. The radiation damage, as characterized by the damage peak and the yield χ min behind the implanted layer, saturates at a dose of approximately 1 × 10 16 ions cm -2 . The oxygen content of the layer is directly proportional to dose until the peak value of the oxygen:silicon ratio reaches 2.0. At higher doses the oxygen concentration only increases in the region between the peak and the surface, resulting in a uniform layer of thickness 2 R p (SiO 2 ). Infrared transmission measurements also indicate that stoichiometric SiO 2 is formed. Annealing at 900 °C has no effect on the RBS spectrum from the implanted layer but the area of the interfacial damage peak is reduced by 60%. Two interesting effects occur: (a) χ min rises to a peak when the oxygen:silicon ratio is approximately unity; (b) the interfacial damage peak decreases with increasing dose once a uniform layer has been formed.