Ion Bombardment Of Ge Research Articles

Single event upset reinforcement technology of DICE flip-flop based on layout design

D flip-flop is the basis of timing logic circuit, and SEMU phenomenon tends to be serious with the integrated circuit process size shrinking to nanometer scale. The anti-SEU ability based on DICE structure for D flip-flop cannot meet the requirements of aerospace engineering. Based on the SEU reinforcement technology of D flip-flop under nano-technology and the SEU mechanism of DICE structure, a layout-level anti-SEU flip-flop design method based on DICE circuit structure is proposed considering the circuit performance, area, power consumption and other resource costs. And then a D flip-flop with SEU resistance is designed by commercial 65 nm process, and the designed flip-flop area is 1.8 times that of commercial structure flip-flop. The function and and radiation simulation results indicate that the establishment time and transmission delay of the flip-flop are equivalent to those of the commercial one, and no SEU occurs under the Ge ion bombardment with the LET threshold of approximately 37 MeV·cm2/mg. The performance of the flip-flop circuit and the ability to resist single particle soft error are excellent. In the anti-radiation ASIC design, the area, wiring resources and timing overhead caused by the reinforcement of the D flip-flop circuit are greatly saved.

Laser Level Scheme of Self-Interstitials in Epitaxial Ge Dots Encapsulated in Si.

Recently, it was shown that lasing from epitaxial Ge quantum dots (QDs) on Si substrates can be obtained if they are partially amorphized by Ge ion bombardment (GIB). Here, we present a model for the microscopic origin of the radiative transitions leading to enhanced photoluminescence (PL) from such GIB-QDs. We provide an energy level scheme for GIB-QDs in a crystalline Si matrix that is based on atomistic modeling with Monte Carlo (MC) analysis and density functional theory (DFT). The level scheme is consistent with a broad variety of PL experiments performed on as-grown and annealed GIB-QDs. Our results show that an extended point defect consisting of a split-[110] self-interstitial surrounded by a distorted crystal lattice of about 45 atoms leads to electronic states at the Γ-point of the Brillouin zone well below the conduction band minimum of crystalline Ge. Such defects in Ge QDs allow direct transitions of electrons localized at the split-interstitial with holes confined in the Ge QD. We identify the relevant growth and annealing parameters that will let GIB-QDs be employed as an efficient laser active medium.

Lasing from Glassy Ge Quantum Dots in Crystalline Si.

Semiconductor light-emitters compatible with standard Si integration technology (SIT) are of particular interest for overcoming limitations in the operating speed of microelectronic devices. Light sources based on group IV elements would be SIT-compatible, but suffer from the poor optoelectronic properties of bulk Si and Ge. Here we demonstrate that epitaxially grown Ge quantum dots (QDs) in a defect-free Si matrix show extraordinary optical properties if partially amorphized by Ge-ion bombardment (GIB). In contrast to conventional SiGe nanostructures, these QDs exhibit dramatically shortened carrier lifetimes and negligible thermal quenching of the photoluminescence (PL) up to room temperature. Microdisk resonators with embedded GIB-QDs exhibit threshold behavior as well as a superlinear increase of the integrated PL intensity with concomitant line width narrowing as the pump power increases. These findings demonstrate light amplification by stimulated emission in a fully SIT-compatible group IV nanosystem.

Dwell-time dependence of irradiation damage in silicon

The influence of the dose rate on the damage creation in silicon has been investigated by means of high current density focused ion beam (FIB) implantation. 70 keV Co and Ge ions with a current density of about 1 A/cm 2 have been implanted into silicon at target temperatures in the range from room temperature to 420°C. The effective dose rate was varied between 10 13 ions/ cm 2 s and about 10 19 ions/ cm 2 s applying different pixel dwell-times from 1 μs to 250 μs. The samples have been investigated using Rutherford backscattering/channeling (RBS/C) combined with a special preparation technique, scanning electron microscopy, micro-Raman spectroscopy and reflectivity measurements. It has been found that at short dwell-times at implantation temperatures of about 400°C the silicon remains crystalline after Co as well as Ge ion bombardment also in the limit of high doses while at long dwell-times the crystal becomes amorphous. These studies of damage accumulation and dynamic annealing reveal that the characteristic time of defect annealing lies in the μs range.

Surface defects created by low energy (20 < E < 240 eV) ion bombardment of Ge(001)

Surface defects created on Ge(001) exposed to low energy Xe ions are characterized by in situ scanning tunneling microscopy (STM). The temperature of the sample during ion bombardment is 165 C and ion energies range from 20 to 240 eV. The ion collisions create defects (vacancies and adatoms) which nucleate and form vacancy and adatom islands. For fixed total vacancy creation, the vacancy island number density increases with increasing ion energy: the vacancy island number density is 1.6 × 10 −20 cm −2 for 40 eV ion bombardment and increases to 4.4 × 10 −20 cm −2 for 240 eV ion bombardment. The increased nucleation rate for vacancies is attributed to clustering of defects. The sputtering yield of Ge(001) is also measured by STM. The sputtering yield for 20 eV ions is approximately 10 −3 per ion but the net yield for surface defects (sum of adatoms and vacancies) is an order of magnitude higher, 10 −2, due to adatom-vacancy pair creation.

Stationary amorphous layer formation during 5 keV Ar+ion bombardment of Ge

Abstract The formation of stationary amorphous layers during high-temperature ion irradiation of semiconductors is considered in the case of 5 keV Ar+ ion bombardment of germanium. The dependence of their thickness on substrate temperature and ion flux is studied. It is shown that the thickness of the amorphous layer does not depend on the initial structural state of a sample. Local critical temperatures for ion-beam induced crystallization and amorphization are introduced and their dependence on depth for the given conditions of ion bombardment is obtained. These two parameters are shown to coincide. A model of defect steady-state formation during ion irradiation is proposed.

Intra-Cascade Surface Recombination of Point Defects During Ion Bombardment of Ge (001)

ABSTRACTLow energy Ar and Xe ion bombardment of Ge (001) produces large numbers of point defects on the Ge surface and in the near-surface regions. Defect concentrations on the surface are detected and quantified in real time during bombardment using in situ Reflection High Energy Electron Diffraction (RHEED). We report the energy dependence of the defect yield for 70–500 eV Ar and Xe ion bombardment, and the temperature dependence of the defect yield (defects/ion) during 200 eV ion bombardment. The defect yield drops rapidly as the substrate temperature during bombardment is varied from 175 K to 400 K. We attribute the yield reduction to surface recombination of adatoms and vacancies produced in the same collision cascade.

Enhancement of Grain Growth In Ultra-Thin Germanium Films By Ion Bombardment

ABSTRACTWe report the enhancement of grain growth in 50 nm-thick Ge films during Ge ion bombardment, or self-implantation, at 500-600 ° C. Conventional and cross-sectional transmission electron microscopy (TEM) indicate that normal grains grow to a columnar structure at considerably lower temperatures than during ordinary thermal annealing. Furthermore, self-implantation-enhanced normal grain growth is found to be very weakly dependent on temperature. The time dependence and temperature dependence of grain growth during self-implantation were compared with data for thermal annealing experiments and suggest that the enhancement results from elastic collisions between ions and atoms located at the grain boundaries.

Atom Ejection in Low Energy Sputtering of Single Crystals of fcc Metals and of Ge and Si

The spatial distribution of atoms ejected from low index planes of Cu, Ni, Au, Al, Ge, and Si have been studied for bombardment by Hg+, Ne+, and Ar+ ions of energies up to 800 ev. In addition, the atom ejection for Hg+-ion bombardment of various Ge planes (12° apart) belonging to the [110] zone has been investigated in detail. For the fcc crystals, ejection was observed in 〈110〉 directions at all energies, in〈100〉 directions at higher energies, and in 〈411〉 directions under certain conditions. The ejection in the 〈110〉 and 〈100〉 directions are interpreted to be the result of focusons intercepting the surface with sufficient energy to cause a surface atom to be ejected. It is shown that a reasonable interpretation of the atom ejection in 〈411〉 directions is that a 〈110〉 focuson may intercept and eject a surface atom which is in a twin position rather than a normal position. For ion bombardment of Ge and Si atom ejection is observed in 〈111〉 and 〈100〉 directions. A possible interpretation is that many of the natural interstitial positions are filled near the surface as a result of the bombardment and that the structure resembles more that of a bcc structure. The systematic deviation in ejection directions from the associated crystallographic direction observed for the Hg+-ion bombardment of various Ge surfaces suggests that the atomic collisions resulting in atom ejection for Ge and Si occur in the outer few surface layers.