Strontium diffusion in feldspars—a laboratory study

Sr90 Radiotracer diffusion studies have been carried out on crystals of orthoclase and microcline using an ion implantation method. The activation energies are consistent with calculations based on mineral age data.

Diffusion of Be, Co and Mn impurities in compound semiconductors and glassy carbon studied by the modified radiotracer technique

The main method of modifying properties of semiconductors is to introduce small amount of impurities inside the material. This is used to control magnetic and optical properties of materials and to realize p- and n-type semiconductors out of intrinsic material in order to manufacture fundamental components such as diodes. As diffusion can be described as random mixing of material due to thermal movement of atoms, it is essential to know the diffusion behavior of the impurities in order to manufacture working components. In modified radiotracer technique diffusion is studied using radioactive isotopes of elements as tracers. The technique is called modified as atoms are deployed inside the material by ion beam implantation. With ion implantation, a distinct distribution of impurities can be deployed inside the sample surface with good con- trol over the amount of implanted atoms. As electromagnetic radiation and other nuclear decay products emitted by radioactive materials can be easily detected, only very low amount of impurities can be used. This makes it possible to study diffusion in pure materials without essentially modifying the initial properties by doping. In this thesis a modified radiotracer technique is used to study the diffusion of beryllium in GaN, ZnO, SiGe and glassy carbon. GaN, ZnO and SiGe are of great interest to the semiconductor industry and beryllium as a small and possibly rapid dopant hasn t been studied previously using the technique. Glassy carbon has been added to demonstrate the feasibility of the technique. In addition, the diffusion of magnetic impurities, Mn and Co, has been studied in GaAs and ZnO (respectively) with spintronic applications in mind.

Thin Film Strain Gauges--an Overview

This review gives a brief description of the historical development followed by the origin and the principle of operation of strain gauges. The features of an ideal strain gauge for measurement purposes and the general classes of strain gauges are given. The remaning part is devoted to an important development in strain gauge technology, namely thin film strain gauges. After highlighting the advantages of thin film strain gauges, a review of current data is given. Detailed description of metallic thin film strain gauges is provided and avaliable information on alloy semiconductor and cermet films for their possible use as strain gauge elements has also been included. The importance of ion implantation in tailoring the properties of strain gauges is highlighted. 33 ref.--AA

Impurity diffusion in bismuth single-crystals

Measurements of impurity diffusion of 86Rb, 90Sr, 133Ba, and 137Cs in single crystal Bi were carried out. Diffusion samples were prepared from single crystal Bi by ion implantation. About 1012-1013 ions were implanted, resulting in surface activities approx =104 cpm. After implantation, specimens were annealed for specified times at 220-265 deg C, and tracer penetration profiles were determined by an electrolytic method. A typical penetration profile for 137Cs in Bi showed a linear relationship for log C vs x in with Fick's law for volume diffusion. Laws of grain boundary diffusion were not obeyed and the order of magnitude of the penetration distances was much less than on a grain boundary mechanism. Results were interpreted in terms of a modified Fischer analysis using a kinetic trapping term. Effective half lengths for trapping at a twin boundary were determined for each impurity.

Numerical simulation of nano-indentation on rough surfaces

Nano-indentation is a technique used to measure various mechanical properties like hardness, Young's modulus and the adherence of thin films and surface layers. It can be used as a quality control tool for various surface modification techniques like ion-implantation, film deposition processes etc. It is important to characterise the increasing scatter in the data measured at lower penetration depths observed in the nano-indentation, for the technique to be effectively applied. Surface roughness is one of the parameters contributing for the scatter. This paper is aimed at quantifying the nature and the amount of scatter that will be introduced in the measurement due to the roughness of the surface on which the indentation is carried out. For this the surface is simulated using the Weierstrass-Mandelbrot function which gives a self-affine fractal. The contact area of this surface with a conical indenter with a spherical cap at the tip is measured numerically. The indentation process is simulated using the spherical cavity model. This eliminates the indentation size effect observed at the micron and sub-micron scales. It has been observed that there exists a definite penetration depth in relation to the surface roughness beyond which the scatter is reduced such that reliable data could be obtained.

向日葵 (Helianthus annuus L.) 种质资源相关的基础研究

向日葵原产自北美,通过人工培育,形成了具有不同遗传多态性的品种,是一种集观赏、药用、食用、油用于一体，经济价值很高的资源植物。前人已经利用传统育种、辐射育种以及现代生物技术手段对向日葵种质资源的开发和保护进行了深入研究，这也加速了向日葵新品种的选育。随着离子注入等新型辐射方式的出现，离子注入对向日葵的诱变育种研究逐渐成为向日葵新品种选育的一个新增长点。另外，作为世界四大油料作物之一，向日葵种子老化问题一直存在于向日葵种质资源保存过程。向日葵种子作为向日葵的主要物质储存库，除了含有丰富的油、脂肪酸外，还含有丰富的维生素E资源。提高向日葵种子维生素E含量可以延长向日葵种子保存时间，也可以提高向日葵的经济价值。本文以向日葵种子为实验材料，分别用蛋白质组学的方法和生理方法对N+注入后向日葵种子、人工衰老向日葵种子以及向日葵种子成熟过程中维生素E代谢进行了初步分析。 对N+注入后向日葵种子蛋白质组变异研究发现，对照种子蛋白中的No.29特异蛋白与MADS盒转录因子HAM59有23.48%的匹配率;处理种子中的No.279特异蛋白与亮氨酸拉链蛋白的同源蛋白HAHB-4有23.20%的匹配率。说明离子注入能引起向日葵种胚蛋白质组水平上的变异，以期对离子注入的诱变机制进行初步探讨，为进一步探讨离子注入对于DNA及蛋白质的是否存在诱变热点提供一些初步的证据。 种子在高温和高含水量情况下曝露数天诱发的加速衰老比一般衰老引起更多的生化分解;另一方面，在长期贮存条件下的低温贮存环境和种子低含水量可能使种子处于玻璃态。种子胞质的极高粘度和低分子运动能够阻止或抑制很多有害过程。尽管种子衰老的生理机制已有大量研究，但衰老过程中的主要过程和相互作用仍未完全清楚。本文报道向日葵种子在较宽范围的含水量和温度条件下的脂过氧化、非酶蛋白糖基化对种子衰老的影响;同时，对种子玻璃态在长期贮存中对生化分解的阻滞作用并由此延长种子存活力也进行了探讨;与此同时我们借用蛋白质组学手段对加速老化的向日葵种子进行蛋白质组变异分析，结果发现随着老化程度的加深，出现部分蛋白含量随之增加，同时老化速率随之下降。通过质谱鉴定发现其中两个蛋白分别与resistance gene analog NBS4和 NBS5具有一定的同源性。因此我们推测，在加速老化过程中，亦可出现一些延缓老化的蛋白质，同时这些蛋白的出现是否标志着加速老化过程中也存在“玻璃态”有待于进一步的证实。 另外，我们以20份向日葵种质资源为实验材料，通过对维生素E含量、含油率、皮壳率以及百粒重的测定及统计分析，试图了解向日葵种质资源中维生素E含量变异及相关数据。结果表明，在20份向日葵种质资源中，油葵的维生素E含量和含油率明显高于食葵;含油率与维生素E含量在0.01水平呈极显著正相关，含油率与百粒重在0.05水平呈显著负相关;百粒重与皮壳率在0.01水平呈极显著负相关。通过初步评价，发现3份富含天然维生素E的向日葵种质。为了提高向日葵种子中维生素E含量，我们对向日葵胚胎发育过程中维生素E的积累以及短时高温对维生素E代谢的影响做了分析。我们发现，生育酚含量在开花后12到33天期间呈线性增长，并于33天后基本达到最大值，直至种子成熟。在上述生育酚增长期，我们将以每7天作为一个时间单位，对向日葵种胚发育过程进行高温处理。我们发现，高温对维生素E积累具有明显的刺激作用（以干重为基础）。但是由于在开花后12到19天之内高温处理会极大的影响干重的增加，因此当温度超过35℃时，生育酚总量还是大大下降的。然而，35℃的高温在向日葵开花后12到19天内并没有影响种胚的干重，而大大提高了单粒种子中的生育酚含量。因此，这些结果说明，我们可以调整播种时间提高向日葵中生育酚的含量，从而提高向日葵油的品质和向日葵种质的价值。

Enhancement of room temperature sub-bandgap light emission from silicon photonic crystal nanocavity by Purcell effect

We report the enhancement of sub-bandgap photoluminescence from silicon via the Purcell effect. We couple the defect emission from silicon, which is believed to be due to hydrogen incorporation into the lattice, to a photonic crystal (PhC) nanocavity. We observe an up to 300-fold enhancement of the emission at room temperature at 1550 nm, as compared to an unpatterned sample, which is then comparable to the silicon band-edge emission. We discuss the possibility of enhancing this emission even further by introducing additional defects by ion implantation, or by treating the silicon PhC nanocavity with hydrogen plasma. © 2011 Elsevier B.V.

Comment on

In a recent letter, Hsieh reported the growth of high-quality Ge epilayers with a SiGe buffer thickness of only 0.45 mu m, a surface root-mean-square roughness of less than 0.4 nm, and a threading dislocation of 7.6 x 10(6) cm(-2) on Si+ pre-ion-implantation Si substrate utilizing of strain relaxation enhancement by point defects and interface blocking of the dislocations. Our comment has focused on x-ray diffraction data shown in Fig. 3 of Ref. 1. We demonstrate that the strain in Ge epilayers is tensile, rather than compressive as misunderstood by the authors. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3003873]

An evidence of defect gettering in GaN

The effect of Neon ion implantation on the structural and optical properties of MOCVD grown GaN was studied. X-ray diffraction and low temperature photoluminescence measurements were carried out on the implanted samples annealed at 900 degrees C. The peak at 3.41 eV exhibited an interesting behavior in as-grown and the implanted samples. Annealing has enhanced the intensity of this peak in as-grown samples, but suppressed in all the implanted samples. Capturing of defects by cavities during gettering process is interpreted as the reason for the observed behavior of this luminescence peak. Implantation dose of 5 x 10(15) ions/cm(2) caused the complete quenching of yellow band luminescence. (C) 2008 Elsevier B.V. All rights reserved.

Structural characterization of mn implanted AlInN

AlInN/GaN thin films were implanted with Mn ions and subsequently annealed isochronically at 750 and 850 degrees C. X-ray diffraction and Rutherford backscattering spectroscopy (RBS) techniques were employed to study the microstructural properties of the implanted/annealed samples. The effect of annealing on implantation-induced strain in thin films has been studied in detail. The strain was found to increase with dose until it reached a saturation value and after that it started decreasing with a further increase in the dose. RBS measurements indicated the atomic diffusion of In, Al, Ga and Mn in implanted samples. The in- and out-diffusion of atoms has been observed after annealing at 750 degrees C and 850 degrees C, respectively. Strong decomposition of the samples took place when annealed at 850 degrees C.

Structural properties of ne implanted GaN

We report a study on the micro-structural changes in GaN due to neon ion implantation using the x-ray diffraction and Raman scattering techniques. An implantation dose of 10(14) cm(-2) was found unable to produce lattice deformation observable by Raman measurements. For higher doses of implantation several disorder activated Raman scattering centers were observed which corroborate the literature. A new dose dependent feature has been recorded at 1595 cm(-1) for higher implantation doses which is suggested to be the vibrational mode of microcavities produced in the lattice.

Effect of annealing on photoluminescence properties of neon implanted GaN

The effect of thermal annealing on the luminescence properties of neon implanted GaN thin films was studied. Low temperature photoluminescence (PL) measurements were carried out on the samples implanted with different doses ranging from 10(14) to 9 x 10(15) cm(-2) and annealed isochronally at 800 and 900 degrees C. We observed a new peak appearing at 3.44 eV in the low temperative PL spectra of all the implanted samples after annealing at 900 degrees C. This peak has not been observed in the PL spectra of implanted samples annealed at 800 degrees C except for the samples implanted with the highest dose. The intensity of the yellow luminescence (YL) band noticed in the PL spectra measured after annealing was observed to decrease with the increase in dose until it was completely suppressed at a dose of 5 x 10(15) cm(-2). The appearance of a new peak at 3.44 eV and dose dependent suppression of the YL band are attributed to the dissociation of VGaON complexes caused by high energy ion implantation.

Mn-AlInN: a new diluted magnetic semiconductor

Mn ions have been incorporated into MOCVD grown Al1-x In (x) N/GaN thin films by ion implantation to achieve the room temperature ferromagnetism in the samples. Magnetic characterizations revealed the presence of two ferromagnetic transitions one has Curie points at similar to 260 K and the other above room temperature. In-diffusion of indium caused by the Mn implantation leads to the partition of AlInN epilayer into two diluted magnetic semiconductor sub-layers depending on the Mn concentration. The Curie temperature of 260 K is assigned to the layer having lower concentration, whereas T (c) above room temperature is assumed to be associated to the layer having higher Mn concentration.

The structure, morphology and Raman scattering study on Mn-implanted nonpolar a-plane GaN films

Dilute magnetic nonpolar GaN films with a Curie temperature above room temperature have been fabricated by implanting Mn ions into unintentionally doped nonpolar a-plane (1 1 (2) over bar 0) GaN films and a subsequent rapid thermal annealing (RTA) process. The impact of the implantation and RTA on the structure and morphology of the nonpolar GaN films is studied in this paper. The scanning electron microscopy analysis shows that the RTA process can effectively recover the implantation-indUced damage to the surface morphology of the sample. The X-ray diffraction and micro-Raman scattering spectroscopy analyses show that the RTA process can just partially recover the implantation-induced crystal deterioration. Therefore, the quality of the Mn-implanted nonpolar GaN films should be improved further for the application in spintronic devices. (C) 2009 Elsevier B.V. All rights reserved.

Room-temperature ferromagnetism and in-plane magnetic anisotropy characteristics of nonpolar GaN:Mn films

Diluted magnetic nonpolar GaN Mn films have been fabricated by implanting Mn ions into nonpolar aplane (1 1 (2) over bar 0) p-type GaN films and a subsequent rapid thermal annealing process. The ferromagnetism properties of the films were studied by means of superconducting quantum interference device (SQUID). Clearly in-plane magnetic anisotropy characteristics of the sample at 10 K were revealed with the direction of the applied magnetic field rotating along the in-plane [0 0 0 1]-axis. Moreover, obvious ferromagnetic properties of the sample up to 350 K were detected by means of the temperature-dependent SQUID. (C) 2009 Elsevier B.V. All rights reserved.