[en] Full text: It is known that the ion implantation of germanium single crystals at room temperature results in drastic alteration of the germanium surface and the formation of cellular relief. Voids were found into the near-surface damage layer. The intersection of these voids with the germanium surface, as result of sputter etching, forms cellular relief. However, exact mechanism responsible for formation of the voids is not known. A 10 and 30 keV Ga⁺ irradiation of Ge {100} crystal at room temperature was carried out using a focused ion beam (FIB) system with a dose in the range 0.5x10¹² to 1.5x10¹⁴ ion/cm². The topology of the modified germanium surface and the structure of the radiation damage was studied using imaging facilities of the FIB systems and transmission electron microscopy. The strong cellular structure of Ge was observed after an ion dose of 3x10¹³ ion/cm². High-resolution TEM showed a complex structure of the implantation induced damage layer. The damage layer showed two distinct regions; an upper part of the damage ∼150 nm thick containing voids and holes, and a lower part - an amorphous region ∼ 30 nm thick. It was also found that the amorphous matrix surrounding the voids contained germanium crystallites with a diameter up to 30 nm. Such crystallites were not found in the lower part of the damaged Ge surface. Apparently, the partial recrystallisation of the damage layer plays a role in the void formation during ion implantation of germanium crystals

[en] Full text: Electrically detected magnetic resonance (EDMR) is a novel way of detecting resonant changes in the magnetoresistance of semiconductors. In most cases that have been studied to date, the resonant change is due to a change in the spin polarisation of recombination centres due to the resonant absorption of microwave radiation in a scanned magnetic field. In that case, EDMR is similar to electron spin resonance (ESR). EDMR is more sensitive than ESR and also it is specific to electrically active paramagnetic centres. In an entirely different form of EDMR, we have observed small, but well-resolved, features in the magnetoresistance of several semiconductors in the absence of microwave radiation. An explanation of some of these feature is provided in terms of a change in the spin polarisation due to a crossing of the Zeeman-split sub-levels of a recombination centre in the scanned magnetic field. The crossing of Zeeman sub-levels has been observed in optically detected magnetic resonance (ODMR) before. In other cases this explanation is not applicable and other possibilities must be considered. The features of a similar, but not the same, type have been observed so far from several devices: silicon Schottky diodes, InGaAs high electron mobility transistors (HEMT's) and most recently from tunnel diodes. The most notable properties of the features are that they are observable at room temperature and depend very sensitively on the orientation of the magnetic field B: the features move progressively over a range from 0.05 T to more than 1 T with angle. The experimental results will be presented and discussed in terms of theoretical models

[en] Full text: Diamond has extreme properties, such as high mechanical hardness, chemical inertness, high thermal conductivity, high refractive index, optical transparency, and a series of well-characterized photoluminescent centers. We demonstrate the pioneering fabrication of cantilever, waveguide and optical cavity three-dimensional microstructures in bulk single-crystal diamond, using a novel lift-off technique. The method involves MeV ion implantation to produce a buried sacrificial layer, followed by pattern milling with a focused keV ion beam and chemical etching of the patterned regions. Three-dimensional structures are thus obtained with well-defined micrometric features, which have remarkable potential applications in nano opto-electronics and quantum computing. Copyright (2005) Australian Institute of Physics

[en] The effect of temperature in the 293-473 K range, on the secondary electron emission (SEE) yield of single crystal and polycrystalline diamond film surfaces is reported. For the polycrystalline films the SEE yield was found to decay as function of electron irradiation dose while for the single crystal an increase occurs first, followed by a decrease. For both surfaces, the SEE yield increases significantly upon heating and obtained a nearly constant value with electron dose at 473 K. These effects are explained as due to the temperature dependence of the electron beam induced hydrogen desorption and surface band bending.

[en] Full text: A Focused Ion Beam miller (FIB) produces a finely focused, energetic beam of gallium ions which may be scanned over the surface of a specimen. At reduced beam currents, the secondary electrons or secondary ions emitted from the specimen surface can be used to form high resolution images. At high beam currents the gallium beam rapidly sputters the specimen surface permitting accurately located subsurface cross-sections to be prepared. Very thin (-100nm) TEM sections can be made of specimens that are difficult to prepare by traditional methods. The FIB is particularly useful for the examination of materials where subsurface microstructure information is required. It is therefore important to assess the influence of ion milling on the specimen structure. Ion beam irradiation of poorly conducting materials may result in the trapping of charge at either pre-existing or irradiation induced defects. The trapped charge produces an electric field within the ion-irradiated micro-volume of specimen which may influence the local structure. This work investigates focused ion beam induced charging of insulating materials using advanced Scanning Probe Microscopy techniques. Kelvin Probe Microscopy (KPM) or Scanning Surface Potential Microscopy (SSPM) is a specialized Atomic Force Microscopy technique in which long-range Coulomb forces between a conductive atomic force probe and a specimen enable the electrical potential at the specimen surface to be characterized with high spatial resolution. A Veeco/ Digital Instruments extended Dimension 3000 Scanning Probe Microscope configured to operate in KPM/SSPM mode, has been used to characterize non-conductive materials exposed to gallium ion irradiation in a FEI x P200 Focused Ion Beam miller. Significant localized residual charging is observed within the gallium implanted micro-volumes of non-conductive materials prior to and following the onset of sputtering. Charge mitigation strategies including coating the specimen with a layer of thin grounded conductive material prior to milling and/ or the use of an electron flood gun during milling have been investigated. The reproducible characteristic surface potentials associated with the trapped charge have been modelled using three dimensional conformal Finite Element Analysis and compared with observed residual potentials. This gives insight into the charging processes during implantation and milling and the resultant spatial distributions of the residual trapped charge. The results of this work have implications for the microanalysis of non-conductive materials processed in Focused Ion Beam millers. Copyright (2003) Australian Microbeam Analysis Society

[en] The effect of temperature on the stability of the secondary electron emission (SEE) yield from ∼100-nm-thick continuous diamond films is reported. At room temperature, the SEE yield was found to decay as a function of electron irradiation dose. The SEE yield is observed to increase significantly upon heating of the diamond surface. Furthermore, by employing moderate temperatures, the decay of the SEE yield observed at room temperature is inhibited, showing a nearly constant yield with electron dose at 200 deg. C. The results are explained in terms of the temperature dependence of the electron beam-induced hydrogen desorption from the diamond surface and surface band bending. These findings demonstrate that the longevity of diamond films in practical applications of SEE can be increased by moderate heating.

[en] The effect of swelling of crystalline Ge irradiated at room temperature with 30 keV Ga⁺ focused ion beam (FIB) was studied by means of in situ FIB imaging, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The swelling occurred in the surface region of amorphous damage layer which was formed during ion irradiation. The degree of swelling reaches values up to 10 times for an implantation dose of ∼10¹⁷ ions/cm². Cross-secitonal TEM examination showed that the swelling is due to formation of a porous layer with a honeycomb structure. (author). 8 refs., 4 figs

[en] In As/GaAs strained-layer superlattices (SLS) grown on a GaAs(100) substrate were studied by both Raman spectroscopy (RS) and transmission electron microscopy (TEM). It was shown that the interfaces inside the superlattice are coherent, but the superlattice-substrate interface contain an orthogonal two-dimensional network of 60 deg; misfit dislocations. Using these experimental data values of elastic strain in individual layers and the average values of the residual elastic strain in SLS were determined. The latter are approximately one order of magnitude higher than theoretically predicted data, which suggests that the relaxation of elastic strains was not fully complete. Subsequent annealing of these structures led to the generation of more misfit dislocations, consistent with further relaxation of elastic strain. Copyright (2000) CSIRO Australia

[en] Although hydrogentated diamond emits exceptionally high numbers of electrons upon single ion impact, the secondary electron yield decays at an extremely rapid rate as a function of ion fluence. We report measurements of this rapid decay at extremely low fluences where the ion tracks are widely separated and explain the results by a model based on the downwards bending of the conduction band edge, due to positive charge trapped within the ion track. The present work demonstrates the importance of charge trapping in explaining the electronic properties of diamond and other wide band gap materials

[en] Carbon ions of MeV energy were implanted into sapphire to fluences of 1x10¹⁷ or 2x10¹⁷ cm^-2 and thermally annealed in forming gas (4% H in Ar) for 1 h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L₁) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L₂) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L₃) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions. These results are compared with our previous work on carbon implanted quartz in which nanodiamond phases were formed only a few tens of nanometers from the surface, a considerable distance from the projected range of the ions, suggesting that significant out diffusion of the implanted carbon had occurred.