Au Ion Beam Research Articles

Damage and Lattice Strain in Ion-Irradiated AlxGai-xAs

AbstractRadiation-induced damage and strain in AlxGai-xAs (x=5 to 1) were investigated by measurements of the lattice parameter using x-ray diffraction. Irradiations employed MeV C, Ar and Au ion beams with a substrate temperature of 80 K. For samples with high Al content, the out-of-plane lattice parameter increased with fluence at low doses, saturated, and then decreased to nearly its original value. The in-plane lattice parameter did not change, throughout. These results were independent of the irradiation particle when scaled by damage energy. For the Al.5Ga.5As samples, however, the out-of-plane lattice parameter increased monotonically with dose to large strains until the layer amorpnized. Selected samples were examined by high resolution and conventional transmission electron microscopy (TEM). Channeling Rutherford backscattering spectrometry (CRBS) was also employed to monitor the buildup of damage in many samples. Recovery of the lattice parameter during subsequent thermal annealing was also investigated.

Interface modification using high energy (MeV) ion beam mixing

Experiments have been carried out to investigate the parameters which can be used to control the mixing profiles, and the width of the intermixed layer, in film-substrate systems which are irradiated by high energy ion beams. Thin films of Cu and Ti were deposited on a variety of substrates such as Si, Ni, Ti, Al, and C. The samples were irradiated by ion beams of Au, Cu, and Si with energies of 1.5–9 MeV, at room temperature, while monitoring the substrate temperature. Typical examples of the RBS spectra are presented, the extent of the contribution of binary collisions on the interfacial mixing is discussed. The experimental and simulation results suggest that the interfacial mixing is dominated by the binary collisions. The width of the mixed layer and the degree of mixing can be controlled by ion beam dose and energy.

Photochemical fine etching using FIB-induced damage in GaAs for in-situ dry processing

We have developed a new FIB maskless microfabrication process using photochemical dry etching. After n-type GaAs (1×10 18/cm 3) was irradiated by focused Be, Si, and Au ion beams, the sample was photochemically etched in HCl gas under a mercury lamp. The FIB-induced damage reduced the etching rate. 0.2 μm-wide fine patterns are successfully formed. The etching rate ratio between the ion implanted (1×10 13 ions/cm 2) and unimplanted regions is about 5. This dose is three or four orders of magnitude smaller than the dose for Cl 2 gas assisted FIB direct etching, and is comparable to the dose needed for organic resist exposure.

Detection of alignment signals for focused ion beam lithography

A detector and the output signal waveforms to be used for alignment in focused ion beam lithography are discussed. It is shown that a microchannelplate (MCP) is suitable for alignment signal detection. Alignment signals for 200-keV Si, 200-keV Be, and 100-keV Au ion beams are studied using the MCP. No deformation of alignment marks is observed in the case of light ions such as Si or Be. As a result, it is demonstrated that alignment can potentially be performed by detecting secondary electrons from the marks.

Contributions to Fusion Research from Studies of Foil-Excited Heavy Ion Beams

XUV spectra in the wavelength region from 5-55 nm have been measured at Brookhaven National Laboratory for foil-excited ion beams of Au, W, Zr, Mo, Fe, and Ti. These atoms are of particular interest in fusion research. In sharp contrast to the wide-ranging time-dependent charge state evolution of heavy ions in a plasma discharge, foil excitation of a heavy ion beam produces relatively well-defined narrow charge-state distributions. Existing accelerators, such as the Brookhaven MP tandems, can produce sufficiently energetic heavy ion beams to span the range of charge states found in present-day tokamaks. The comparison of spectra from beam-foil excitation and tokamak plasmas can therefore be used to infer the average ion and charge state makeup of the plasma discharge. Such comparisons with Au, W, and Mo features in tokamak spectra are discussed and spectra for Zr and Fe (which are expected contaminants in new tokamaks) are presented. Additional contributions to fusion research from beam-foil experiments are demonstrated. These include: wavelengths and identifications for lines which can be resolved in plasma spectra and direct determinations of radiative lifetimes and absorption oscillator strengths for these transitions which are used to determine impurity concentrations in plasmas.