Correlation between Defects and Electrical Performances of Ion-Irradiated 4H-SiC p–n Junctions

In this study, 4H-SiC p–n junctions were irradiated with 700 keV He+ ions in the fluence range 1.0 × 1012 to 1.0 × 1015 ions/cm2. The effects of irradiation were investigated by current–voltage (I–V) and capacitance–voltage (C–V) measurements, while deep-level transient spectroscopy (DLTS) was used to study the traps introduced by irradiation defects. Modifications of the device’s electrical performances were observed after irradiation, and two fluence regimes were identified. In the low fluence range (≤1013 ions/cm2), I–V characteristics evidenced an increase in series resistance, which can be associated with the decrease in the dopant concentration, as also denoted by C–V measurements. In addition, the pre-exponential parameter of junction generation current increased with fluence due to the increase in point defect concentration. The main produced defect states were the Z1/2, RD1/2, and EH6/7 centers, whose concentrations increased with fluence. At high fluence (>1013 ions/cm2), I–V curves showed a strong decrease in the generation current, while DLTS evidenced a rearrangement of defects. The detailed electrical characterization of the p–n junction performed at different temperatures highlights the existence of conduction paths with peculiar electrical properties introduced by high fluence irradiation. The results suggest the formation of localized highly resistive regions (realized by agglomeration of point defects) in parallel with the main junction.

Порообразование в тонких пленках германия при имплантации ионов Ge-=SUP=-+-=/SUP=-

The results of a study of the morphology of the nanostructured by ion implantation germanium films are presented. The film samples were grown using the magnetron sputtering method in an ultrahigh vacuum and then were irradiated with Ge+ ions of 40 keV energy in the fluence range of (1.8–8)×10(16) ion/cm2. Using the scanning electron microscopy it was found that in the implanted germanium volume the vacancy complexes with a diameter of 50–150 nm gradually form and come to the surface upon reaching a certain implantation fluence, forming a developed relief of the irradiated films.

Spectral Ellipsometry of Cobalt-Ions Implanted Silicon Surface

Monocrystalline silicon wafers implanted by cobalt ions with energy of 40 keV at a fluence range from 6.6×1012 to 2.5×1017 Co+-ion/cm2 were investigated by optical spectroscopic ellipsometry. By comparison of experimental data with modeling it is shown that the ellipsometric measurements are accurate and reliable method for monitoring of a low-dose ion implantation process.

Preparation and heavy-ion irradiation effects of Gd2CexZr2−xO7 ceramics

A number of compositions with the general stoichiometry of Gd2CexZr2−xO7 (0 ≤ x ≤ 2) ceramics have been synthesized and received irradiation tests at room temperature with Xe20+ ions in a broad fluence range.

Tailoring Structural Properties of Polyethylene Terephthalate (PET) by 200 keV Ar+ Implantation

In the present work, our aim is to reveal the effect of Ar+implantation on the structural behaviour of Polyethylene terephthalate (PET) using Fourier Transform Infrared and UV-Visible Spectroscopic techniques. PET specimens were implanted with 200 keV Ar+ions in the fluence range of 1x1015to 1x1017ions cm-2. The structural changes have been observed due to change in the position and intensity of the bands in the FTIR spectra of both implanted and unimplanted specimens. A continuous decrease in optical energy gap (from 3.63 eV to 1.48 eV) and enhancement in Urbach energy (from 0.29 eV to 3.70 eV) with increasing ion dose have been observed. The structural changes have been correlated with the optical parameters observed in PET specimens as a result of implantation.

Raman scattering study of Si nanoclusters formed in Si through a double Au implantation

ABSTRACTA sequential two step 32 keV Au implantation and 1.5 MeV Au irradiation technique has been used to synthesize Si nanoclusters (NCs) in Si. The low energy amorphising implantation has been carried out over a fluence range of (1 – 100) × 1015 cm−2 while the high energy recrystallizing irradiation fluence was fixed at 1 × 1015 cm−2. Samples were further annealed in air at temperatures between 500° to 950° C for a fixed annealing time of 1 hr and were characterized using Raman scattering at an excitation wavelength of 514.5 nm. Results on as-implanted and irradiated samples indicate formation of strained NCs in the top amorphised layer. Annealing around 500°C has been found to result in strain relief after which the data could be well explained using a phonon confinement model with an extremely narrow size distribution.

Defects in High Energy Ion Irradiated 4H-SiC

The defects produced by 7.0 MeV C+ irradiation in 4H-SiC epitaxial layer were followed by Deep Level Transient Spectroscopy, current-voltage measurements and Transmission Electron Microscopy in a large fluence range (109-51013 ions/cm2). At low fluence (109 -1010 ions/cm2), the formation of three main level defects located at 0.68 eV, 0.98 eV and 1.4 eV below the conduction band edge is detected. The trap concentration increases with ion fluence suggesting that these levels are associated to the point defects generated by ion irradiation. In this fluence range the leakage current of the diodes does not change. At higher fluence an evolution of defects occurs, as the concentration of traps at 0.68 eV and 1.4 eV decreases, while the intensity of the level at 0.98 eV remains constant. In this fluence range complex defects are formed and an increase of a factor five in the leakage current is measured.