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Artefacts in germanium transmission electron microscope specimens prepared by focused ion beam milling
Published in A. G. Cullis, P. A. Midgley, Microscopy of Semiconducting Materials 2003, 2018
Fig. 3: Bright field TEM images of the bottom-wall of the trench milled at 30 keY and lOOOpA a) the overall structure, b) this region at higher magnification. A is the Ge substrate B the fully amorphous region and C the more complex region containing crystallites. Figure 4 shows the bright field TEM images of the side-wall and bottom-wall images of a section milled into germanium using a beam current of 250 pA and a beam current of 10 keY. Overall the damage layers generated were similar in structure to those milled at 30 keY. That is, the side-wall was amorphous, but only -12 nm in thickness. The bottom-wall layer was again more complex and consisted of an amorphous layer adjacent to the crystalline substrate and a more complex region, containing crystallites and small voids between the amorphous region and the gold protective layer. Again, this layer was thinner than the same layer milled at 30 keY. The total thickness of this bottomwall was- 26 nm. In contrast to the sections milled at 30 keY the voids were only a few nanometres in diameter. Other studies have shown that damage layers in, for example, silicon or GaAs are similarly, reduced by the use of a lower energy beam (Walker and Broom 1997). The thickness of the damage layers observed by TEM was compared with values calculated using the Stopping and Range of Ions in Matter (SRIM) software (Zeigler 2000). Calculations were made for Ga ion traces, range, straggle and vacancy distribution. The side-wall damage layers were calculated to be 13 nm, for a 30 keY beam energy, and 7 nm, for a 10 keY beam energy. For these calculations the angle of incidence was taken 4.5°, which corresponds to the average slope angle in FIB prepared TEM samples. For 10 keY the thickness of bottom-wall damage layer, where the beam is normal to the implanted surface, was calculated to be II nm. Calculated data for total penetration depth (range plus straggle) for 30 keY Ga ions in Ge was found to be 26 nm. It is clear that the calculated thickness layers are somewhat smaller than those observed by TEM. The difference between the experimental and theoretical data can be explained by considering the dynamic nature of FIB milling. The SRIM model describes accurately the events in the ion collision cascade for target material with a particular density (in the case of Ge 5.35 g/cm3 ). However, during the FIB milling process the initially formed damage layer is not static and moves dynamically inside the target. Some of energetic ions collide with the atoms in the near-surface region of the amorphous damage layer and knock them out. However, other ions penetrate through this amorphous layer and cause further amorphisation of the crystalline germanium substrate. It can also be noted from the data obtained by SRIM calculations that germanium has a very large number of vacancies per incident Ga ion. That means that the density of the amorphous Ge formed by Ga irradiation is reduced with respect to the original Ge target. The Ga ions lose less energy when they penetrate such heavily damaged, vacancy-rich area, and this can produce displacement events at a greater distance than in a
Bistatic RCS reduction caused by radionuclide layer for spherical object
Published in Waves in Random and Complex Media, 2023
The emitted alpha particles with an energy of about 5.45 MeV from the radioactive nucleus Americium-241, and their deposition energy at a short distance, can ionize the air around and produce a high density of electrons in surface layers. The codes used to calculate the range and deposition energy are Geant4 and SRIM. Geant4 is a toolkit for simulating the passage of particles through matter and is capable of handling all physics processes including electromagnetic, hadronic, and nucleus–nucleus interactions which are indispensable to calculating three-dimensional dose distributions and deposition energies in air and ion therapy [29]. The SRIM Monte Carlo simulation code is widely used to compute several parameters relevant to ion beam implantation and ion beam processing of materials [30].
Formation of bubbles and blisters in hydrogen ion implanted polycrystalline tungsten
Published in Radiation Effects and Defects in Solids, 2018
Jiandong Zhang, Jiangtao Zhao, Weilin Jiang, Xingcai Guan, Haibo Peng, Zihua Zhu, Tieshan Wang
The Monte Carlo code named Stopping and Range of Ions in Materials (SRIM) is a widely used method for the calculation of ion damage and distribution in materials (13). In this study, SRIM-2010 code was also used for the simulation with two typical (40 keV and 6 keV) implantations. The displacement threshold energy was 90 eV (14). ‘Full damage cascade’ model was selected in order to calculate the damage details. In case of some unknown errors as reported in (15), Kinchin-Pease model was also used for comparison. The results prove that full damage cascade model is good in this study. Figure 1 shows the simulated curves of H and damages. Gauss-like profiles of the implanted H ions was observed. The projected ranges are at ∼108 nm for 40 keV H+ ions and ∼32 nm for 6 keV H+ ions, respectively. The simulation also indicates that higher energy H ions can create more damages in the material.
The effects of high-energy ion irradiations on the I–V characteristics of silicon NPN transistors
Published in Radiation Effects and Defects in Solids, 2018
A. P. Gnana Prakash, M. N. Bharathi, Vinayakprasanna N. Hegde, T. M. Pradeep, N. Pushpa, Ambuj Tripathi
The high-energy ion while passing through the semiconductor material deposits its energy through different kinds of interactions and scattering mechanisms. The energy deposited by the passage of the ion in the target material results in two major effects such as ionization and displacement of target atoms. The Stopping and Range of Ions in Matter (SRIM) simulations have been used to understand the type of damages that the incident ions can induce in the target material and the device (7). The variation of electronic energy loss and nuclear energy loss versus depth in the transistor for different LET ions is shown in Figure 2. The energy loss and range of different LET ions in the transistor structure estimated from SRIM simulations are given in Table 1. The range of the ions traversed inside the transistor decreases with an increase in the atomic number of the incident ions. From the SRIM calculations, it is clear that the chosen ions pass through the active region of the transistor (∼20 µm from the top surface).