Zhang Chong-Hong

Mechanical Properties and Defect Evolution of Kr-Implanted 6H-SiC

Specimens of silicon carbide (6H-SiC) were irradiated with 5 MeV Kr ions (84Kr19+) for three fluences of 5×1013, 2 ×1014 and 1× 1015 ions/cm2, and subsequently annealed at room temperature, 500°C, 700°C and 1000°C, respectively. The strain of the specimens was investigated with high resolution XRD and different defect evolution processes are revealed. An interpretation of the defect evolution and migration is given to explain the strain variation. The mechanical properties of the specimens were studied by using a nano-indentation technique in continuous stiffness measurement (GSM) mode with a diamond Berkovich indenter. For specimens irradiated with fluences of 5×1013 or 2×1014 ions/cm2, hardness values exceed that of un-implanted SiC. However, hardness sharply degrades for specimens irradiated with the highest fluence of 1×1015 ions/cm2. The specimens with fluences of 5×1013 and 2×1014 ions/cm2 and subsequently annealed at 700°C and 500°C, respectively, show the maximum hardness value.

Raman Spectroscopy of Irradiation Effect in Three Carbon Allotropes Induced by Low Energy B Ions

Irradiation effect in three carbon allotropes C60, diamond and highly oriented pyrolytic graphite (HOPG) induced by 170 keV B ions, mainly including the process of the damage creation, is investigated by means of Raman spectroscopy technique. The differences on irradiation sensitivity and structural stability for C60, HOPG and diamond are compared. The analysis results indicate that C60 is the most sensitive for B ions irradiation, diamond is the second one and the structure of HOPG is the most stable under B ion irradiation. The damage cross sections σ of C60, diamond and HOPG deduced from the Raman spectra are 7.78 × 10−15, 6.38 × 10−15 and 1.31 × 10−15 cm2, respectively.

Effects of Helium and Oxygen Common Implantation in Silicon Wafer

Defect engineering for SiO2 precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen (SIMOX). Cavities are created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120keV 8.0 ? 1016 cm-2 O ions. The O ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectional transmission electron microscopy (XTEM), Fourier transform infrared absorbance spectrometry (FTIR) and atomic force microscopy (AFM) measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation.

Study of He-induced nano-cavities as sinks of oxygen for forming silicon-on-insulator

In the present work, a Cz-Silicon wafer is implanted with helium ions to produce a buried porous layer, and then thermally annealed in a dry oxygen atmosphere to make oxygen transport into the cavities. The formation of the buried oxide layer in the case of internal oxidation (ITOX) of the buried porous layer of cavities in the silicon sample is studied by positron beam annihilation (PBA). The cavities are formed by 15 keV He implantation at a fluence of 2 x 10(16) cm(-2) and followed by thermal annealing at 673 K for 30 min in vacuum. The internal oxidation is carried out at temperatures ranging from 1073 to 1473 K for 2 h in a dry oxygen atmosphere. The layered structures evolved in the silicon are detected by using the PBA and the thicknesses of their layers and nature are also investigated. It is found that rather high temperatures must be chosen to establish a sufficient flux of oxygen into the cavity layer. On the other hand high temperatures lead to coarsening the cavities and removing the cavity layer finally.

Investigation of the dependence of fraction of damage phase in garnet irradiated by 1 GeV Ar ions on electronic energy loss and irradiation dose

Abstract The dependence of fraction of damage phase on electronic energy loss (Se) and irradiation dose (φt) in 1 GeV Ar ion irradiated garnet was investigated by means of sample-tilting X-ray diffraction (STD), Mossbauer spectroscopy and saturation magnetization measurement. It is found that the fraction of damage phase Fd is a linear function of the product of Se and ln(φt) under a certain irradiation dose. The slopes of the lines are decreasing with the increase of irradiation dose. This regular phenomenon suggests that the influence of irradiation dose on the creation of damage phase is increasing with the increase of irradiation dose in the electronic stopping power regime.

Surface morphology of GaN bombarded by highly charged 126 Xe q + ions

N-type GaN films bombarded with different highly charged 126Xeq+-ions（9≤q≤30） at room temperature was studied by atomic force microscopy. The experimental results show that when q exceeds the threshold value 18, remarkable swelling turns into obvious erosion in the irradiated area. On the other hand, surface disorder of GaN films strongly depends on the charge state q of ions, incident angle and ion influence, and the damage behavior of films is unrelated to the kinetic energy within the scope of experimental parameters（180 keV≤Ek≤600 keV）.For q=18, the surface morphology of the films almost does hot change at normal incidence, and at incidence angle of 30° relative to the film surface, there appears small-scale swelling in irradiated region and a low step forms between the irradiated and un-irradiated regions. For q 18, film surface is etched, forming a deep dump with a high step with the increase of ions influence. Unambiguous indentations relevant to the ion influence on the step appear. Furthermore, the step height is proportional to the ion influence approximately and is much higher for tilted incidence than normal incidence.

Surface Disorder of GaN Irradiated by Highly Charged Ar q + -Ions *

The surface damage to gallium nitride films irradiated by Arq+ (6 ≤ q ≤ 16) ions at room temperature is studied by the atomic force microscopy. It is found that when charge state exceeds a threshold value, significant swelling was turned into obvious erosion in the irradiated region. The surface change of the irradiated region strongly depends on the charge state and ion fluence. On the other hand, surface change is less dependent on the kinetic energy nearly in the present experimental range (120keV≤ Ek ≤ 220 keV). For q ≤ 14, surface of the irradiated region is covered with an amorphous layer, rough and bulgy. A step-up appears between the irradiated and un-irradiated region. Moreover, the step height and the surface roughness are functions of the ion dose and charge state, and increase with the increase of dose and charge state. Especially at and near boundary, a sharp bump like ridges in irradiated areas is observed, and there appear characteristic grooves in un-irradiated areas. For q = 16, surface of the irradiated region was etched and erased.

Surface Erosion of GaN Bombarded by Highly Charged 208Pbq+-Ions

Surface change of gallium nitride specimens after bombardment by highly charged Pbq+-ions (q = 25, 35) at room temperature is studied by means of atomic force microscopy. The experimental results reveal that the surface of GaN specimens is significantly etched and erased. An unambiguous step-up is observed. The erosion depth not only strongly depends on the charge state of ions, but also is related to the incident angle of Pbq+-ions and the ion dose. The erosion depth of the specimens in 60? incidence (tilted incidence) is significantly deeper than that of the normal incidence. The erosion behaviour of specimens has little dependence on the kinetic energy of ion (Ek = 360,700keV). On the other hand, surface roughness of the irradiated area is obviously decreased due to erosion compared with the un-irradiated area. A flat terrace is formed.