Pei-Ran Zhu

Range distributions of ion‐implanted fluorine in Hg1−xCdxTe, CdTe, and Pb1−xSnxTe

Depth profiles of ion‐implanted fluorine in Hg1−xCdxTe, CdTe, and Pb1−xSnxTe have been measured by use of the 19F(p,αγ)16O resonance nuclear reaction at 872.1 keV with width Γ=4.2 keV. In order to obtain the true range distribution of implanted fluorine from the experimental excitation yield curve, a convolution calculation method is presented, from which the range distribution parameters such as the average projected range RP, the projected range straggling ΔRP and the skewness of the projected range distribution SK were obtained. These experimental range parameters were compared with those obtained by a theoretical calculation and by use of the trim89 program, and shows that for all the materials studied here the experimental RP values agree with the theoretical and the trim values very well but the experimental range straggling ΔRP are larger than those obtained by the theoretical calculation and the trim89. This phenomenon may be attributed to the enhanced diffusion during the ion implantation.

Anomalous ion channeling in InGaAs/GaAs strained heterojunction

An ion beam with different incident energies E was used to analyze a 500‐A‐thick In0.25Ga0.75As strained epitaxial film grown on GaAs (100) by molecular beam epitaxy. Ion channeling angular scans about 〈110〉 axis were carried out in (100) plane. When E is 5.8 MeV, the angular misalignment between 〈110〉 channels of the top layer and the substrate was 0.90°. We can calculate the planar strain of the epilayer, which is 1.62%. When incident ion energy was decreased, anomalous phemomena were observed in the angular scan profiles of the substrate. When E is 3.0 MeV, a serious asymmetry appeared in axial scan profile of the substrate; When E is 1.2 MeV, the angular misalignment reduced to 0.60°, and the critical angle for channeling of the substrate is 1.25° which is much larger than that of the epilayer, 0.95°. The physical mechanism giving rise to these phenomena is discussed, and the causes and conditions for these phenomena taking place were pointed out.

Lattice disorder in LiNbO3 crystals induced by MeV Cu+ implantation

The effects of 1 MeV Cu ion implantation in LiNbO3 crystals have been investigated using the Rutherford backscattering/channeling technique. The samples have been implanted with doses ranging from 5×1014 ions/cm2 to 2×1015 ions/cm2. The damage profiles have been deconvoluted from Rutherford backscattering spectra after considering the energy spreading due to difference of stopping power between nonchanneled and channeled particles. The energy dependence of the scattering cross section and stopping power have also been taken into account. The damage profiles have compared with TRIM’89 (Transport of Ions in Matter, version 1989) code calculation. For the lowest dose (5×1014 ions/cm2) implantation, the damage profile is in agreement with the defect profile calculated using the trim code. The damage peak is located shallower than the theoretical ion mean projected range, but the damage spread is larger than the ion spread. For higher dose implantations, a broadening of the damage profiles is observed, probabl...

Effects of forming cavities on the lattice quality and carrier profile in the B doped silicon

We have used electron microscopy to investigate the microstructure of Ni80Fe20/Cu magnetic multilayers which were synthesized by dc magnetron sputtering. Columnar structure was found in the specimen with and without giant magnetoresistance (GMR). All the columnar crystallites (CCs) originate from the Fe buffer layer on silicon wafer or glass substrate and penetrate though all the multilayers up to the surface of the film. The lateral size of the CCs ranges from 10 to 30 nm. Cross-sectional high-resolution electron microscopy study shows that the CCs are single-crystal-like with fcc structure resulting from the epitaxial growth of NiFe and Cu sublayers. Electron diffraction contrast imaging and electron energy filtered elemental mapping confirmed that multilayer nature is maintained throughout the entire NiFe/Cu film. Grain boundaries between CCs can be the most likely place where NiFe or Cu bridging will occur. Columnar structure was also found in a Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve film. The possible influence of the columnar crystalline structure on the GMR related problems is discussed. The microstructure results revealed in this article provide useful information for the GMR property investigation of NiFe/Cu based metallic multilayers

REDUCTION OF CRYSTALLINE DISORDER IN MOLECULAR-BEAM EPITAXY GAAS ON SI BY MEV ION-IMPLANTATION AND SUBSEQUENT ANNEALING

Molecular beam epitaxy GaAs films on Si, with thicknesses ranging from 0.9–2.0 μm, were implanted with Si ions at 1.2–2.6 MeV to doses in the range 1015–1016 cm−2. Subsequent rapid infrared thermal annealing was carried out at 850 °C for 15 s in a flowing N2 atmosphere. Crystalline quality was analyzed by using Rutherfold backscattering/channeling technique and Raman scattering spectrometry. The experimental results show that the recrystallization process greatly depends on the dose and energy of implanted ions. Complete recrystallization with better crystalline quality can be obtained under proper implantation and subsequent annealing. In the improved layer the defect density was much lower than in the as‐grown layer, especially near the interface.

Reduction of secondary defects in BF2 implanted Si(100) by ion beam defect engineering

Reduction of secondary defects in 50 keV, 2×1015 BF2/cm2 implanted Si(100) has been studied by Rutherford backscattering and channeling technique. Secondary defects with high densities have been found in BF2 implanted Si(100) after thermal annealing and rapid thermal annealing. However, a noticeable reduction of secondary defects in BF2 damaged region was observed when a buried amorphous layer was formed by an additional irradiation of 1.0 MeV Si+ ions prior to annealing (i.e., ion beam defect engineering process).

Effects of ion beam defect engineering on carrier concentration profiles in 50 keV P+‐implanted Si(100)

Shallower carrier concentration profiles in 50 keV P+‐implanted Si(100) after annealing at 1000 °C for 1 h have been observed when a buried amorphous layer was formed by an additional irradiation of 1.0 MeV Si+ ions prior to annealing (i.e., ion beam defect engineering process). The secondary defects formed in the MeV Si+ damaged region act as gettering sites for the collection of interstitials from the shallower depths which are responsible for the transient diffusion of P, and therefore the transient diffusion of P is reduced and the carrier concentration profiles become shallower.

Topography of skeletal muscle ryanodine receptors studied by atomic force microscopy

Tapping mode atomic force microscopy (AFM) was used to investigate the topography of isolated ryanodine receptors of rabbit skeletal muscle (RyR1) both in air and in a buffer. In air, images fourfold symmetric in appearance were obtained. Two different configurations could be distinguished in the AFM topography of single RyR1s, depending on whether there was a center protrusion. In the buffer, even though square images of RyR1s were discerned, the detailed topography of RyR1 appeared different from that in air. Possible reasons for this are discussed

Characteristics of CrSi2 and Cr(Ni)Si2 synthesis in MEVVA ion source implantation and post-annealing processes

We investigate the formation of silicide layers in(111) Si wafers with a high-current implanter. Cr ions form a disilicide layer of low sheet resistance. If the sample is also implanted with Ni, the total number of Cr atoms is reduced by sputtering, and the previously prepared CrSi2 layer is disordered. However, a stable textured Cr1-xNixSi2 phase can be prepared by proper annealing. Above 1150 degrees C the ternary phase segregates into CrSi2 and NiSi2. Thus the introduction of Ni can result in well-defined and stable Cr1-xNixSi2 alloys

Gettering effects in BF2‐implanted Si(100) by ion‐beam defect engineering

The gettering effects of ion‐beam defect engineering (IBDE) in BF2‐implanted silicon have been studied. It has been shown that the IBDE technique may be useful in the improvement of the properties of BF2‐implanted silicon. The gettering layer introduced by MeV Si ion irradiation and formed during the process of thermal annealing collects not only impurities but also simple defects. Thus, it effected (1) reductions of secondary defects and F impurity accumulation in the BF2‐doped region; (2) reduction of the anomalous diffusion of B atoms; and (3) enhancement of the electrical activation of B atoms.