Small metal particles in the range of a few nanometers in diameter are seen to progressively disorder when the 100 keV electron beam of a Scanning Transmission Electron Microscope (STEM) is held stationary on the particle. The diffraction pattern of the individual particle is seen to progress from an initial array of indexable diffraction spots to a mixture of diffraction spots and amorphous-like rings and finally to rings with no persistent diffraction spots. After the electron beam is removed, the particles will recrystallize after minutes or hours. Only particles below a critical size are seen to fully disorder. We have observed this in Platinum, Palladium, Rhodium, and Iridium and based on our model of disordering process believe it is a universal effect. It has also been observed with a Platinum Ruthenium alloy. We discuss the mechanism of this disordering and the structure of the resulting disordering particle for the case of Platinum clusters.

Epitaxial regrowth of isolated amorphous zones, created in Ge by implantation with 50 keV Xe+ ions, was stimulated at room temperature by using electron beams with an energy below that required to create Frenkel pairs. The process was studied by using transmission electron microscopy combined with an automatic computer image analysis program, and the regrowth was characterized by determining the shrinkage rate of the effective radius of individual zones. The effective radius decreases approximately linearly with electron dose. The regrowth rate of irregular shaped amorphous zones is fast initially and slows as the shape of the amorphous zone becomes more regular. Only one regrowth rate is found for amorphous zones with a regular shape. The regrowth rate increased with decreasing energy below the threshold displacement voltage, suggesting that electronic excitations are able to induce epitaxial growth.

Amorphous LaPO4, EuPO4, GdPO4, ScPO4, LuPO4, and fluorapatite [Ca5(PO4)3F] were irradiated by the electron beam in a transmission electron microscope. Irradiations were performed over a range of temperatures from −150 to 300 °C, electron energies from 80 to 200 keV, and current densities from 0.3 to 16 A/cm2. In all cases, the materials crystallized to form a randomly oriented polycrystalline assemblage. Crystallization is driven dominantly by inelastic processes, although ballistic collisions with the target nuclei can become important at energies higher than 175 keV, particularly in apatite. Using a high current density, crystallization is so fast that continuous lines of crystallites can be “drawn” on the amorphous matrix.

Highly oriented pyrolitic graphite (HOPG) was irradiated with 1.8 MeV electrons at 45° and near grazing (86°) angles of incidence. For doses up to 1016 cm−2 the surface for the case of 45° incidence, observed by scanning tunnelling microscopy (STM), remained the same as the original sample showing only the usual periodic atomic corrugation. For near grazing incidence, at a dose of 5×10−2 cm−2, nm-hillocks are observed, some elongated along the direction of the beam incidence. These are attributed to the effects of single electron-carbon interactions in the top surface layers. At a dose of 5×1014 cm−2 (near grazing incidence) STM observations show an anomalously large (period 2.5 to 17 nm) superperiodicity superimposed on the normal 0.246 nm atomic spacing of graphite. This Moiré-like pattern suggests that the corrugations are electronic as well as topographic in origin. We propose that near grazing incidence electron irradiation causes a break-up of the surface layers into fragments, largely retaining the six-fold atomic rings, that rotate by a small angle resulting in the observed pattern by interaction with the deeper bulkstructure layers.

Radiation effects on insulators have been extensively studied in terms of radiation induced damage. However, little work has concentrated on in situ surface modification during irradiation and the evolution of surface relaxation after the termination of irradiation. In this work, 1.3 keV electrons and 1.2536 keV Mg Kα X-ray photons were applied to investigate radiation effects on surface structural changes during irradiation and relaxation. The microstructure and composition of lead silicate glass were investigated in situ in an ultra-high-vacuum (UHV) environment by X-ray Photoelectron Spectroscopy (XPS). Similar surface radiation effects were observed using both types of radiation which included permanent metallic lead separation from the glass network resulting from Pb-O bond breaking, bimodal distribution of the 0 is XPS signal due to bridging and non-bridging oxygens, gradual increase of total lead and silicon concentrations and gradual decrease of oxygen concentration during relaxation. Different radiation effects for electron beam and X-ray photons were also observed. For photon irradiation, silicon and lead continuously accumulated while the oxygen on the surface continuously decreased during irradiation and relaxation. In the case of electron irradiation, both silicon and lead were depleted from the surface during irradiation and accumulated during relaxation. Opposite concentration changes were observed for oxygen; it increased during irradiation and decreased during relaxation. The experimental results are discussed in terms of charge effects, secondary electron yield, field-enhanced diffusion, non-bridging oxygens and nucleation of metallic lead.

The argon excimer laser provides 9.8-eV photons that readily surmount the electronic bandgap energy of SiO2 (∼9.0 eV), directly generating excitons in a single-photon absorption process. We have shown by Si L2,3 (Si 3s→2p) X-ray emission spectroscopy, Si 2p X-ray photoelectron spectroscopy and Raman spectroscopy that this absorption process is responsible for silicon precipitation in the silica. The X-ray emission studies further show that the silicon precipitates are crystalline, forming in highest concentration in 120–230 nm layer beneath the laserirradiated surface. Silicon precipitation was not observed on samples irradiated with 146-nm krypton excimer radiation due to a smaller 8.5-eV photon energy that is below the silica bandgap.

MgO and LiNbO 3 single crystals were bombarded with GeV swift heavy ions (Pb, Gd) and 30MeV C60 clusters to study the damage production induced by giant electronic processes at stopping power up to 100keV/nm. The defect creation was characterized by optical absorption, transmission electron microscopy (TEM) and Rutherford backscattering spectrometry in channeling geometry (RBS-C). In MgO point defects (F type centers) and extended defects (dislocation loops) were created by ionization processes in addition to those associated with nuclear collisions. The F-center concentration induced by electronic energy excitations was studied at different temperatures and as a function of the particle electronic energy losses. TEM revealed that dislocation loops were produced close to the particle trajectories and amorphization was never observed. On the opposite, in LiNbO3 continuous amorphous tracks were evidenced above a threshold near 5keV/nm. The dependance of this effects with various solid state parameters will be discussed.