Analysis of ion implanted diamond

Ion implantation allows controlled introduction of impurities into diamond. A basic problem is to determine if the implanted layers are dominated by substitutional doping or radiation damage effects. Optical and electrical measurements on the implanted diamonds revealed (1) a degradation of the band-gap and sample coloration, (2) no optical absorption levels which would be characteristic of hydrogenic ionization levels, (3) resistivity activation energies of 0.2 to 0.3 eV independent of the ion specie, and (4) no measurable Hall Effect.

Phosphorous implanted layers in diamond were analyzed by means of the channeling technique. It was shown that (1) the diamond retained the implanted phosphorous atoms during a vacuum anneal at 950°C which restored crystalline order, (2) the implanted phosphorous atoms did not assume either substitutional or tetrahedral interstitial sites, (3) the measured projected range for 70 keV phosphorous in diamond of 450 ± 115 Å was consistent with theoretical range calculations and (4) a stable monolayer of oxygen atoms (5.5 × 10¹⁵/cm²) exists on the {111} surface of implanted and annealed diamond. The results of the crystal analysis show that these electrical and optical properties are dominated by radiation damage and not substitutional doping mechanisms.     

PAC investigation of implanted semiconductors

The TDPAC investigation of compound semiconductors in which the probes were recoil implanted provides valuable statements to the microscopic environments of implanted atoms. In all cases considered the probe surroundings anneal nearly completely. The extent and annealing behaviour of radiation damage is connected with the binding properties of the tetrahedrally coordinated substances as expressed by the spectroscopic ionicity parameter f_i.     

Ion mixing in multilayer films and the doping of the near-surface layers of polycrystalline substrates under irradiation by ion beams with a wide energy spectrum

Various factors influencing ion mixing efficiency are considered. It is established that the energy transfer from ions and primary knocked-on atom films to subsequent displacement cascades underlies the penetration of atoms from multilayer films into a polycrystalline substrate. The penetration of implanted atoms to great depths is in this case determined by the defect density, the radiation induced migration of the implanted atoms, and their interaction with the atoms of the matrix. All of these factors can be described in terms of the isotropic mixing model. It is shown that when doped by atoms from multilayer films, gradient layers form that are determined by the range of radiation in the substrate of the atoms to be implanted and their migration under irradiation by an ion beam with a wide range of energies.     

Formation of Cu nanoparticles in GaAs using MeV ion implantation followed by thermal annealing

Analytical electron microscopy, high-resolution X-ray diffraction and combined Rutherford backscattering spectrometry and channeling experiments have been used to investigate the radiation damage and the effect of post-implantation annealing on the microstructure of GaAs(100) single crystals implanted with 1.00 MeV Cu⁺ ions to a dose of ≈ 3×10¹⁶ cm^-2 at room temperature. The experiments reveal the formation of a thick and continuous amorphous layer in the as-implanted state. Annealing up to 600 °C for 60 min does not result in the complete recovery of the lattice order. The residual disorder in GaAs has been found to be mostly microtwins and stacking fault bundles. The redistribution of implanted atoms during annealing results in the formation of nano-sized Cu particles in the GaAs matrix. The X-ray diffraction result shows a cube-on-cube orientation of the Cu particles with the GaAs lattice. The depth distribution and size of the Cu particles have been determined from the experimental data. A tentative explanation for these results is presented. Received: 15 February 1999 / Accepted: 18 February 1999 / Published online: 28 April 1999     

Diffusion Processes in Semiconductor Structures During Microwave Annealing

We present the results of experimental studies of the influence of microwave radiation on the diffusion processes in two different semiconductor materials, namely, InGaAs heterostructures with quantum wells and boron-ion implanted silicon. The experiments were performed in a 30 GHz gyrotron device for microwave processing of materials. We compare the results of heterostructure annealing under microwave and thermal heating. It is found that under microwave heating, the coefficient of In–Ga interdiffusion in InGaAs heterostructures is about an order of magnitude smaller than that under thermal heating at the same temperatures, while the activation energy of diffusion is approximately the same for both heating regimes. In boron-ion implanted silicon, the sheet resistance after annealing at a higher microwave power turns out to be lower than that after annealing at the same temperature and a lower power. This indicates that the microwave field exerts a nonthermal effect on electric activation of dopant atoms. The results show the possibility of optimization of the microwave-annealing regimes to obtain the maximum electric activation at a limited diffusion spreading of the density profile of implanted atoms.     

Superconducting properties and structural transformations of nitrogen implanted molybdenum films

Evaporated Mo-layers have been implanted with nitrogen ions to maximum fluences corresponding to a concentration of 33 at.%. The implantations lead to an enhancement of the superconducting transition temperature T_c up to 9.2 K and to structural transformations. Both effects are attributed to radiation induced disorder stabilized by the implanted impurity atoms; in particular the increase of T_c is thought to be due to the formation of impurity-defect complexes; channelling experiments support the idea of locally stabilized complexes.     

Mechanism for the enhanced diffusion of charged oxygen ions in SiO2

Based on real-space multigrid electronic structure calculations, we find that a double Si-O-Si bridge structure is the lowest energy configuration of interstitial oxygen ions (O(-) and O(2-)) in SiO2, where two additional Si-O bonds are formed with almost no interaction between the interstitial and host O atoms, while the peroxy linkage is the most stable structure for neutral interstitial O. We propose a diffusion mechanism of interstitial O ions generated from molecular O2 under UV radiation, and find extremely low energy barriers of 0.11--0.27 eV for migration in the form of the double-bridge structure, in good agreement with enhanced oxidation experiments.     

The influence of distortions on apparent surface radiation damage cross sections in Si

It is suggested, that high radiation damage cross sections for Si surfaces as measured by RBS and channeling can be explained by assuming a distortion of lattice atoms around defects. We give both experimental and theoretical support for a specific surface sensitivity to this effect in ion scattering experiments.     

纳米晶LaNiAl薄膜充氦技术研究

采用离子束辅助磁控溅射方法沉积出了纳米晶LaNiAl膜和纳米晶渗氦LaNiAl膜（膜厚约10 m）,通过调节Ar-He气氛的比例可控制纳米晶膜中的含氦量（He/LaNiAl的原子分数5.7%~13.8%）,通过该方法引入到LaNiAl金属薄膜中的氦量远高于采用球磨法制备的纳米LaNiAl粉中的含氦量。研究结果表明:渗氦LaNiAl膜中的氦含量（原子分数）可达13.9%,氦在膜的深度方向分布均匀;热解析分析恒温条件下沉积的渗氦膜的起始释放温度为848 K,最高释放温度为1407 K,主释放峰为1080 K,初步确定了氦主要是以团簇的形式存在于在纳米晶膜中。     

Modification of thin oxide films on Be,Si, Al,Ti, Zr,and W under bombardment by He<Superscript>+</Superscript> and Ar<Superscript>+</Superscript> ion beams with a broad energy spectrum

Data on the distribution of Be, Al, Ti, Fe, Cu, Zr, Mo, and W atoms implanted in oxide film on metal substrates by ion mixing under the action of He⁺ and Ar⁺ ion beams with a broad energy spectrum, with average energy of 10 keV, and with radiation doses up to 1 × 10²¹ ion/cm² are presented. It is shown that layers with different concentration gradients of implanted atoms form in a thin oxide layer due to simultaneous implantation, but their concentration decreases dramatically to the background value at the oxide-metal interface. Analysis of experimental data suggests that the migration of implanted atoms takes place by means of the diffusion mechanism and is determined by the parameters of physicochemical interaction of implanted atoms with substrate atoms.     

Mössbauer study of 57Fe in GaAs and GaP following 57Mn+ implantation

Ion implantation provides a precise method of incorporating dopant atoms in semiconductors, provided lattice damage due to the implantation process can be annealed and the dopant atoms located on regular lattice sites. We have undertaken ⁵⁷Fe emission Mössbauer spectroscopy measurements on GaAs and GaP single crystals following implantation of radioactive ⁵⁷Mn^?+? ions, to study the lattice sites of the implanted ions, the annealing of implantation induced damage and impurity–vacancy complexes formed. The Mössbauer spectra were analyzed with four spectral components: an asymmetric doublet (D1) attributed to Fe atoms in distorted environments due to implantation damage, two single lines, S1 assigned to Fe on substitutional Ga sites, and S2 to Fe on interstitial sites, and a low intensity symmetric doublet (D2) assigned to impurity–vacancy complexes. The variations in the extracted hyperfine parameters of D1 for both materials at high temperatures (T?> 400 K) suggests changes in the immediate environment of the Fe impurity atoms and different bonding mechanism to the Mössbauer probe atom. The results show that the annealing of the radiation induced damage is more prominent in GaAs compared to GaP.     

Multi-step damage accumulation in irradiated crystals

This article presents a model of damage accumulation in irradiated crystals. This model is based on the assumption that the damage accumulation occurs through a series of structural transformations triggered by the destabilization of the current structure of crystals. Formal equations describing the damage accumulation build-up and experimental assessment of the model are presented and discussed in the framework of the actual knowledge of radiation effects in oxide crystals (yttria-stabilized zirconia (YSZ) and magnesium-aluminate spinel (MAS)), silicon carbide crystals and zirconia implanted nickel crystals.     

Hydrogen incorporation behaviour and radiation damage in proton bombarded InP single crystals

Abstract

In proton bombarded InP single crystals the incorporation behaviour of different hydrogen isotopes is studied in relation to implantation induced radiation defects. Investigations of the fluence dependence (D = 10¹⁶-10¹⁸ cm^?2), of the depth profile and of the annealing behaviour (T _an = 300–1000 K) of hydrogen incorporation and of damage density indicate that only a small fraction of the implanted hydrogen is chemically bonded to host lattice atoms. These bonded hydrogen atoms saturate dangling bonds at defect sites.     

Effect of collisions on the resonance fluorescence spectrum

The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.     

Diffusion effects in ion implanted germanium

During isochronal anneal sequences the number of Hg, Tl and Bi atoms implanted into Ge has been found to decrease. This decrease occurs for all three species and has been observed for samples implanted at room temperature as well as for hot implants (300—350°C). The decrease starts at anneal temperatures of 350—550°C. Similar results have been obtained for In and Sb implanted Ge. For samples implanted with Hg to doses leading to amorphous layers, the decrease in the number of implanted atoms seems to be related to the reordering of the amorphous layer. The experiments show that no diffusion of the implanted atoms into the bulk material occurs and the decrease observed is attributed to be a diffusion of the atoms to the surface followed by outdiffusion, thermal etching or both.     

Location and depth profiling of Ne atoms implanted in a Nb crystal using a resonant nuclear reaction

Trapping of Ne by radiation induced defects is shown through the depth-profiling of Ne implanted into Nb crystals using the ²⁰Ne(p, γ)²¹ Na reaction. A channeling study shows that implanted atoms occupy octahedral interstices in niobium. The change of the Ne profile with further irradiation by other ions is attributed to radiation enhanced diffusion of Ne.     

Hyperfine interactions of impurities in defect sites in ion-implanted metals

The lattice location of ion-implanted radioactive isotopes in metals and their interactions with defects in their own radiation damage cascade are of importance for studies of the hyperfine interactions of such probe atoms by nuclear methods. Recent results from Mössbauer and PAC experiments in particular are reviewed. Emphasis is put on lattice site identifications, which can be inferred from measured lattice-dynamical and hyperfine interaction parameters of probe atoms. Some general conclusions on the hyperfine interactions in interstitial- and vacancy-type complexes are drawn.     

惰性气体在固体中的扩散和释放理论

本文给出了一个描述在各种固体材料中离子注入的惰性气体的扩散和从表面释放的模型。在这个模型中,同时考虑了各种缺陷和辐照损伤与惰性气体原子的相互作用,根据这个模型,给出了一组描写惰性气体原子的扩散方程,并给出了这组方程的解析解。与实验测量比较表明,这个模型能很好地描写惰性气体从固体表面释放的特性。用最小二乘法将理论释放曲线拟合于实验释放曲线,从而给出一个确定各种陷阱中心的激活能和归一化浓度的方法。 关键词：     

Role of many-electron dynamics in high harmonic generation

High harmonic generation (HHG) in many-electron atoms is studied theoretically. The breakdown of the frozen-core single active electron approximation is demonstrated, as it predicts roughly the same radiation amplitude in all noble gases. This is in contradiction with experiments, where heavier noble gases are known to emit much stronger HHG radiation than lighter ones. This experimental behavior of the noble gases can be qualitatively reproduced when many-electron dynamics, within a simple approximation, is taken into account.     

Negative muons as solid state probes

Abstract

It is shown that the use of negative muons as solid state probes is complicated by the de-excitation scheme of muonic atoms. A comparison with some recent radiation damage experiments suggest that the μ^? atom (at least in silicon) is displaced to an interstitial position.