Investigations on the effect of argon ion bombardment on the structural and optical properties of crystalline gallium antimonide

The effects of bombardment of 250 keV argon ions in n-type GaSb at fluences 2×10¹⁵ and 5×10¹⁵ ions cm^?2 were investigated by high-resolution X-ray diffraction (HRXRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). HRXRD studies revealed the presence of radiation-damaged layer (strained) peak in addition to the substrate peak. The variation in the lattice constant indicates the strain in the bombarded region. The out-of-plane (?_⊥) and in-plane strains (?_|) determined from the profiles of several symmetric and asymmetric Bragg reflections, respectively, were found to change with the ion fluence. Simulations of XRD patterns using dynamical theory of X-ray scattering (single-layer model) for the damaged layer yielded good fits to the recorded profiles. FTIR transmission studies showed that the optical density (α·d) of GaSb bombarded with different fluences increases near the band edge with increase in ion fluence, indicating the increase in the defect concentration. The density of the defects in the samples bombarded with different fluences was in the range of 3.20×10²¹–3.80×10²¹ cm^?3. The tailing energy estimated from the transmission spectra was found to change from 12.0 to 58.0 meV with increasing ion fluences, indicating the decrease of crystallinity at higher fluences. SEM micrographs showed the swelling of the bombarded surface of about 0.33 μm for the fluence of 2×10¹⁵ ions cm^?2, which increased to 0.57 μm for the fluence of 5×10¹⁵ ions cm^?2.     

The influence of ion bombardment on emission properties of small dust grains

Dust grains that are present in many plasma and vacuum systems and in the space usually carry a non-negligible charge. Their charging significantly depends on surface properties of the grain material. In cold plasma, charging is mainly given by electron attachment, nevertheless, when plasma becomes hot, other processes (secondary electron emission, field emission, etc.) take place. Emission properties of the grain surface could be modified by grain baking or by ion bombardment. Our study is carried out at the dust charging experiment dealing with a single dust grain electro-dynamically levitated in a 3D quadrupole trap. The grain can be exposed to the ion beam in the energy range of 100 eV–5 keV and to the electron beam in the energy range of 100 eV–10 keV. We have chosen He⁺ and Ar⁺ ions for the surface treatment and the observed influence on the surface properties is discussed in terms of secondary emission. A non-negligible shift of the secondary electron emission yield, as well as a change of energy distribution of secondary electrons, were measured after Ar⁺ bombardment. A preliminary study suggests that the effects of He⁺ and Ar⁺ are comparable.     

Effect of Ar bombardment on the electrical and optical properties of low-density polyethylene films

The influence of low-energy Ar ion beam irradiation on both electrical and optical properties of low-density polyethylene (LDPE) films is presented. The polymer films were bombarded with 320 keV Ar ions with fuences up to 1×10¹⁵ cm^?2. Electrical properties of LDPE films were measured and the effect of ion bombardment on the DC conductivity, dielectric constant and loss was studied. Optically, the energy gap, the Urbach’s energy and the number of carbon atoms in a cluster were estimated for all polymer samples using the UV–Vis spectrophotometry technique. The obtained results showed slight enhancement in the conductivity and dielectric parameters due to the increase in ion fluence. Meanwhile, the energy gap and the Urbach’s energy values showed significant decrease by increasing the Ar ion fluence. It was found that the ion bombardment induced chain scission in the polymer chain causing some carbonization. An increase in the number of carbon atoms per cluster was also observed.     

The influence of ion species on ion bombardment induced preferential orientation

Abstract

Vacuum-deposited Cu specimens were implanted with 40 keV Cu⁺, Ni⁺, Ne⁺, Kr⁺ and Xe⁺ ions in an electromagnetic isotope separator. The specimens were investigated for texture by X-ray diffraction techniques on implanted as well as non-implanted areas of the same specimen. It was found that a preponderance of ?110? crystallographic axes parallel to the incident beam develops during irradiation but that the intensity of the effect is dependent on the ion species in an apparently unpredictable way. A previously suggested channelling mechanism for the origin of the effect is discussed in the light of the present findings and it is concluded that modifications to the proposed mechanism is needed to accommodate these results. It is further shown that certain implications of the results presented here could have an important bearing on ion bombardment related phenomena such as ion ranges, sputtering and materials modification by ion implantation.     

The in situ cleaning of specimens in the field ion microscope by argon ion bombardment

The extensive adoption of argon bombardment cleaning techniques for specimens used in LEED and Auger studies, and the frequent, and often difficult, requirement of preparing field ion emitters, and their supports, free from contamination, led to the investigation of in situ argon ion bombardment of specimens in the field of ion microscope, both from the point of view of the efficiency of the cleaning process, and the investigation of ensuing surface and lattice damage, a task to which the technique of field ion microscopy is particularly appropriate.Experiments were carried out in some detail for tungsten specimens, and subsequently extended to the hexagonal metal, rhenium, with a view to obtain information on the thermally annealed end forms of such metals. In both cases, very small radius clean thermally annealed specimens could be prepared.     

Ellipsometry and the clean surfaces of silicon and germanium

The anomalous ellipsometric effects, which occur upon chemical adsorption of gases on clean silicon and germanium surfaces have been determined in the wavelength region 0.34–1.8 μm. The effects are ascribed to the removal of a transition layer with optical constants different from the crystalline bulk values. Within the scope of this model the optical constants of the transition layer proved to be similar to those of the corresponding amorphous materials. The differences in optical constants between crystalline material on the one hand and amorphous material and transition layer on the other, could be attributed to the presence of dangling or distorted bonds.     

Modifications in physical,optical and electrical properties of tin oxide by swift heavy Au8+ ion bombardment

Tin oxide thin films were deposited by a novel technique called as modified-SILAR. The preparative parameters were optimized to obtain good quality thin films. As-deposited films were annealed in O₂ atmosphere for 1 h at 500 °C. The annealed films were irradiated using Au⁸⁺ ions with energy of 100 MeV at different fluencies of 1 × 10¹¹, 1 × 10¹², 5 × 10¹² and 1 × 10¹³ ions/cm² using tandem pelletron accelerator. The irradiation-induced modifications in tin oxide thin films were studied using XRD, AFM, optical band gap, photoluminescence and I–V measurements. XRD studies showed formation of tin oxide with tetragonal structure. AFM revealed uniform deposition of the material with increase in grain size after irradiation. Decrease in band gap from 3.51 eV to 2.82 eV was seen with increases in fluency. A decrease in PL intensity, and an additional peak was observed after irradiation. I–V measurements showed a decrease in resistance with fluency.     

Diffusion of tin over clean silicon surfaces

Diffusion of tin over the (111), (100), and (110) silicon surfaces has been studied by Auger electron spectroscopy and low-energy electron diffraction. The diffusion mechanisms have been established, and the temperature dependences of the diffusion coefficients have been obtained.     

Study of the electrical and optical properties of silicon containing oxygen precipitates

The properties of n-type silicon with oxygen precipitates introduced by three-stage annealing were studied by the electron beam induced current (EBIC) method, deep-level transient spectroscopy (DLTS), and photoluminescence (PL). The presence of extended defects with concentration of ≤10⁹ cm^?3 is revealed by the EBIC method. The concentration of electrically active defects formed in silicon due to oxygen precipitation is estimated from the EBIC contrast and is compared to that obtained from the DLTS data. Comparing the spectra of samples with oxygen precipitates with those of plastically deformed crystals, we can assume that the DLTS and PL spectra of silicon with oxygen precipitates are mainly determined by dislocations.     

微晶硅薄膜沉积过程中的等离子体光学与电学特性研究

采用空间分辨光发射谱和傅里叶变换功率阻抗分析仪研究了衬底偏压和辉光功率对微晶硅薄膜沉积过程中的等离子体光学与电学特性的影响.研究表明：在交流偏压(AC)、悬浮(floating)、负直流加交流(-DC＋AC)偏压下,Hα发射强度空间分布规律相似,平均鞘层长度相等;正直流加交流(＋DC＋AC)偏压和接地(grounded)时Hα发射强度显著增强,并存在双峰(double layers)现象.增大功率,Hα发射强度也随着增大,并在17W与22W之间产生跳变.电学测试发现功率增大,等离子体电阻降低,电抗降低,电 关键词： 等离子体 光发射谱 衬底偏压 辉光功率     

Diffusion of silver over atomically clean silicon surfaces

The diffusion of silver the (111), (100), and (110) silicon surfaces is studied by Auger electron spectroscopy and low-energy electron diffraction. The mechanisms of diffusion over the (111) and (110) surfaces are revealed, and the temperature dependences of diffusion coefficients are measured. An anisotropy of silver diffusion over the (110) surface is detected.     

Resonant scattering of phonons by adsorbates on clean silicon surfaces

We used Phonon Surface Scattering Spectroscopy (PSSS) to study excitations of adsorbates in the far infrared region from 100 eV up to 3 meV. We investigated the scattering of pulses of monochromatic phonons by thin films of H₂O, D₂O and Ne deposited in situ onto laserannealed Si(100)-surfaces. For all substances we observed a broad scattering at coverages below one monolayer and a strong resonant scattering at about 3 monolayers. The resonance frequency decreased with increasing coverage. The reasons for the resonances are discussed. Because of the lack of any observable isotope effect between H₂O and D₂O, the possibility of tunneling states in these layers can be excluded. Instead, we conclude that a lateral vibrational mode of the adlayer is responsible for the resonance effect. Corresponding calculations by means of continuum elasticity theory describe the scattering behaviour very well if similar elastic constants are used for all film substances.     

Study on optical and electrical properties of gold-doped silicon fabricated by femtosecond laser

Microstructured silicon (Si) materials have been fabricated by femtosecond (fs) laser ablation and have been hyperdoped with gold (Au) impurities. The ablated Si materials showed large and thermostable infrared absorption at 1.1–2.5 μm wavelengths, which was contributed by sub-band absorption and laser-induced defects absorption. The Au–Si alloy was formed after laser irradiation onto the Au-coated Si surface, which was determined by XRD characterization. Using N-type Si substrate, the fabricated Au-doped Si performed lower sheet carrier density due to the self-compensation effect between deep donor and acceptor energy lever of Au in bulk Si material. From Hall measurement, both the p- and n- types of Au-doped Si samples can be obtained by controlling the type of Si substrate.     

Influence of argon ion bombardment on the formation of intermetallic compounds in the nickel-aluminum system

The formation of Ni _x Al _y intermetallic compounds in two-layer (Ni/Al) structures (nickel films deposited on aluminum substrates in vacuum) under bombardment by Ar⁺ ions has been studied experimentally. The method based on Rutherford backscattering of He⁺ ions is used to demonstrate that argon ion bombardment causes the formation of intermetallic compounds in the near-surface layer. The thickness of the intermetallic layer formed in the near-surface region substantially exceeds the projective ion path. The composition and thickness of the intermetallic layer depend mainly on the implantation dose and the substrate temperature, rather than on the ion current density. In the intermetallic layer, the content of nickel increases with increasing temperature. It has been established that, in the absence of bombardment, intermetallic phases are not observed at temperatures lower than T = 400°C and that, in the presence of bombardment, the Ni₃Al intermetallic layer arises at a temperature of 320°C.     

The influence of atomic steps on the photoelectric properties of clean cleaved silicon as derived from the surface photovoltage

The correlation of structural and electrical properties of clean silicon surfaces cleaved in UHV was investigated quantitatively by the surface photovoltage, using light with an energy larger than the band gap of silicon. The surface photovoltage, which is a function of band bending and recombination probability, depends strongly on the appearance of atomic steps. The additional surface states vary with density and crystallographic orientation of the steps as well as with adsorption of oxygen. The experimental facts can be explained by accepting a shift of the Fermi level at the surface towards the valence band due to edge atoms. By measuring the change of sign of the surface photovoltage of crystals with various dopings an exponential temperature dependence of the ratio of the recombination probabilities r_v/r_c for transitions from and into the Surface states has been derived.