Ion implantation effects in single crystal Si investigated by Raman spectroscopy

A study of the effects of Ar ion implantation on the structural transformation of single crystal Si investigated by confocal Raman spectroscopy is presented. Implantation was performed at 77 K using 150 keV Ar⁺⁺ with fluences ranging from 2 × 10¹³ to 1 × 10¹⁵ ions/cm². The Raman spectra showed a progression from crystalline to highly disordered structure with increasing fluence. The 520 cm^?1 c-Si peak was seen to decrease in intensity, broaden and exhibit spectral shifts indicating an increase in lattice disorder and changes in the residual stress state. In addition, an amorphous Si band first appeared as a shoulder on the 520 cm^?1 peak and then shifted to lower wavenumbers as a single broadband peak with a spectral center of 465 cm^?1. Additionally, the emergence of the a-Si TA phonon band and the decrease of the c-Si 2TA and 2TO phonon bands also indicated the same structural transition from crystalline to highly disordered. The Raman results were compared to those obtained by channeling RBS.     

Ion implantation doping and electrical conductivity enhancement of C60 films

Pristine C₆₀ films sublimed onto sheet mica were implanted with 20 keV K⁺ ions and I⁺ ions at doses of 1.0 × 10¹⁶/cm², 3.0 × 10¹⁶/cm² and 5.0 × 10¹⁶/cm², and with 20 keV Ar⁺ ions at a dose of 5.0 × 10¹⁶/cm². The distributions of dopants were studied using Rutherford backscattering spectrometry (RBS). The temperature dependence of sheet resistivity of the films was investigated applying a four-probe system. It was proposed that the conductivity enhancement of K⁺ implanted C₆₀ films was due to the implanted ions in the films, while for I⁺ implanted C₆₀ films, both implanted I⁺ ions and irradiation effects of the ions contributed to the enhancement of conductivity.     

离子注入玻璃

离子注入和离子束分析技术在半导体和金属改性中已获得广泛应用,近年来又开始应用于绝缘体。在1981年第一届绝缘体辐照效应国际会议(REI-81)上,美国Sandia实验室Arnold和意大利Chinellato等发表离子注入玻璃效应的初步研究。Mazzoldi曾应用核反应分析对玻璃辐照效应进行了详细研究。 带电粒子辐照玻璃引起网状损伤并改变了表面化学成分。钠玻璃经离子注入后产生钠离子迁移,Na迁移有两种不同机构,在低质量离子辐照时以电子阻止本领为主,此时钠受到和     

离子注入法掺杂聚乙炔的初步探索

聚乙炔(CH)x是一种简单的共轭有机导电高分子材料。1975年日本白川首先用高浓度的Ti(OBu)_4-AlEt_3体系在-78℃下定向聚合得到了均匀的、具有高结晶度的顺式(CH)x薄膜。1977年白川与美国MacCDiarmid等合作,发现掺杂能改善(CH)x的导电性能。后来又发现掺入不同的杂质可使(CH)x显示n型或P型半导体的特性。聚乙炔薄膜具有物理上准一维金属膜型的一些特殊性质,因而引起物理学家的广泛兴趣。1980年美国Su、Schrieffer和Heeger提出了聚乙炔的孤立子(Soliton)导电模型,并用这种模型成功地阐述了一些实验现象。(CH)x的原料便宜,合成简单,具有广阔的应用前景。人们预期可以把聚乙炔应用于制备太阳能电池、蓄电池及塑料半导体器件等。     

Ion implantation of rare earth ions for light emitters

We discuss the excitation and deexcitation processes for solid state optical emitters. At present, there is considerable interest in depositing a material system, which is compatible to silicon microelectronics processing and which emits electroluminescence (EL). We will compare the EL results of rare earth doped transistors in silicon with doped insulators and doped wide bandgap semiconductors, especially Er in Si (a source for 1.5 μm) as well as Er and Tb in SiO₂, Si₃N₄ and AIN, which are sources for infrared and visible light. The most impressive results are achieved by RE doped GaN film devices, which cover the entire visible spectrum.     

Ion implantation in 4H-SiC

Silicon carbide offers unique applications as a wide bandgap semiconductor. This paper reviews various aspects of ion implantation in 4H-SiC studied with a view to optimise ion implantation in silicon carbide. Al, P and Si ions with keV energies were used. Channelling effects were studied in both a-axis and c-axis crystals as a function of tilts along major orthogonal planes and off the major orthogonal planes. Major axes such as [0 0 0 1] and the and minor axis like the showed long channelling tails and optimum tilts for minimising channelling are recommended. TEM analyses of the samples showed the formation of (0 0 0 1) prismatic loops and the loops as well,in both a and c-cut crystals. We also note the presence of voids only in P implanted samples implanted with amorphising doses. The competing process between damage accumulation and dynamic annealing was studied by determining the critical temperature for the transition between crystalline and amorphous SiC and an activation energy of 1.3 eV is extracted.     

Ion beam synthesis and doping of photonic nanostructures

Optically-active silica nanowires are produced by metal-induced growth on silicon substrates using ion-implantation, with two different strategies employed for their fabrication. The first is based on Er implantation of nanowires produced by a thin-film Pd catalyst layer, and the second employing implanted Er as both the catalyst and dopant. The luminescence properties of the resulting Er-doped silica nanowires are reported and compared with similarly implanted fused silica samples. Comparison shows that the luminescence lifetime of Er is increased by incorporation within the nanowires due to a reduction in the density of available optical states in these structures. Additional details of the synthesis, structure and properties of these functionalised nanowires are also presented.     

Ion implantation damage recovery in GaN

We present a method of ion implantation doping of GaN, which permits reduced residual damage. The method consists of performing implantation in several steps with annealing between each step. Residual damage was analyzed by RBS/channeling and compared to a traditional implantation and annealing procedure. Better lattice recovery is clearly achieved using the alternating implantation and annealing approach. We attribute the efficient recovery to smaller damage amounts introduced during each implantation step, as well as to suppression of secondary defect formation.     

Ion implantation distributions in inhomogeneous materials

A simple, approximate, analytical technique for calculating implanted ion depth distributions in inhomogeneous materials is presented. The central concept in the procedure is the method of equivalent atomic stopping (MEAS) wherein an atom of type k in the target is replaced by ϵ_k equivalent atoms of a preselected standard species. The target, when viewed as a collection of “equivalent standard atoms” is therefore uniform and thus existing techniques for obtaining depth distributions in the equivalent medium can be applied. The constants ϵ_k are shown to be related to range parameters in uniform targets of atoms of type k. The approximation involved in MEAS is examined for the case of low energy implantation by inspection of the properties of Winterbon's generalization of the transport equation. Practical techniques for evaluating the accuracy at higher energies are presented. The method is applied to light and heavy ion implantation into a target consisting of alternating layers of amorphous silicon and germanium, and the results are compared with TRIM calculations. This method is particulary valuable for the initial estimation of appropriate parameters for implantation into complex, layered targets.     

慢正电子探针研究离子注入硅（100）产生的缺陷及其退火行为

用慢正电子探针分别检测了Ｐ＋注入和Ｐ注入Ｓｉ（１００）的两组样品。与基底样品相比较，注入样品中的缺陷导致了正电子湮没参数的显著变化。由湮没线形参数的变化拟合了两组样品注入损伤的深度分布、缺陷对正电子的捕获系数，讨论了Ｐ＋和Ｐ注入损伤缺陷的差别和它们在退火过程中的不同行为。     

Surface modification of Natural Rubber by ion implantation: Evidence for implant doping

Ion implantation is one of the most powerful and well-known technique for surface modification in polymers. Thin films of Natural Rubber were modified by the implantation of 60 keV N⁺ ions to the fluences of 10¹¹–10¹⁵ cm⁻². The electrical conductivity measurements of irradiated sample show 10 orders of magnitude compared to pristine state. Along with conductivity change there was a noticeable change in color to a dense shiny black for the most highly conducting films. The analysis of temperature dependence of dc electrical conductivity data reveals a three-dimensional variable range hopping mechanism. The microstructural evolution of the virgin and ion-beam modified samples was investigated by spectroscopic analysis such as UV/Vis & FTIR. These spectral studies gave evidence for the production of conjugate double bonds, which is a clear cut indication of implant doping. This is an important result since ion implantation usually does not produce doping in polymeric materials and only a few reports about the possibility of implant doping in polymers are available. The significant aspect of this study is that this confirms, the Natural Rubber’s potential to be used as a microelectronic device material. Also an attempt has been made to compare the conductivity enhancement in Natural Rubber by chemical and implant doping.     

Ion microbeam applications in semiconductors

Microbeam techniques and applications to semiconductor analysis are briefly reviewed. Special microbeam requirements and limitations for channeling analysis using MeV He microbeams are discussed, including conditions to minimise beam damage to Si and GaAs. Finally, channeling contrast microscopy is described, together with the application of this technique to the analysis of phase transformations and impurity redistribution in locally laser annealed Si.     

Photoluminescence induced by Si implantation into Si3N4 matrix

Up to the present, photoluminescence (PL) was obtained from near stoichiometric or amorphous Si nitride films (SiN_x) after annealing at high temperatures. As a consequence, the existence of PL bands has been reported in the 400–900 nm range. In the present contribution, we report the first PL results obtained by Si implantation into a stoichiometric 380 nm Si₃N₄ film. The Si excess is obtained by a 170 keV Si implantation at different temperatures with a fluence of Φ = 10¹⁷ Si/cm². Further, we have annealed the samples in a temperature range between 350 and 900 °C in order to form the Si precipitates. PL measurements were done using an Ar laser as an excitation source, and a broad PL band basically centered at 910 nm was obtained. We show that the best annealing condition is obtained at T_a = 475 °C for the samples implanted at 200 °C, with a PL yield 20% higher than the obtained at room temperature implantation. Finally, we have varied the implantation fluence and, consequently, the Si nanocrystals size. However, no variation was observed nor in the position neither in the intensity of the PL band. We concluded that the PL emission is due to radiative states at the matrix and the Si nanocrystals interface, as previously suggested in the literature.     

半绝缘GaAs材料中的Si、Be双重离子注入

GaAs集成电路要求FET有一致的夹断特性,而半绝缘GaAs衬底的质量对Si全离子注入的MESFET有着重大影响。这是由于高阻衬底中的Cr在离子注入和高温退火后的再分布,注入后载流子分布出现翘尾,使部分器件呈现出异常输出特性,表现为夹断电压偏高,小电流时跨导偏低,难以获得均匀的夹断电压。在N型有源层之下,用离子注入工艺形成一个隐埋的P型层,可以大大改善夹断电压的均匀性。已有报道,通过在沟道层和衬底之间引入一P型层,亚微米栅GaAs MSFET的短沟道效应有效地被抑制了,背栅效应对于GaAs集成电路无疑是有害的,模拟计算也表明,使用近补偿的衬底材料或缓冲层可使背栅沟道电容减至最小。     

绿豆种胚中离子注入深度的研究

通过ＳＥＭ和ＳＩＭＳ检测到了离子注入以后绿豆种胚内部的铜元素和钛元素的浓度随深度的分布一形貌变化，说明了离子注入诱发为是带电粒子直接作用的结果。     

Structural changes of Si surfaces by nitrogen implantation using plasma based ion implantation

Nitrogen ion implantation to Si wafers is carried out by a plasma based ion implantation (PBII) and the compositional and structural changes of the Si surfaces are examined as a function of implantation time by energy dispersive X-ray spectrometer (EDX), Raman and Fourier Transform Infrared (FT-IR) spectroscopy. The implantation time is varied from 10 min to 7 h. From the results of EDX measurements, the N concentration is increased with increasing implantation time up to 1 h, but it is not significantly increased at further increase of implantation time. In the Raman spectra, the sharp peak from Si crystal is decreased in intensity and the small peaks from a-Si and/or a-SiN_x appear after N ion implantation. On the other hand, in the FT-IR spectra, a broad peak assigned to Si–N bonds appears after N ion implantation. The result of RBS measurement indicates that the N/Si ratio is approximately 1.3. Judging from these results, it is suggested that a-SiN_1.3 is formed as a surface layer on Si wafer by N ion implantation using PBII system.     

Metal ion implantation in inert polymers for strain gauge applications

Metal ion implantation in inert polymers may produce ultra-thin conducting films below the polymer surface. These subsurface films are promising structures for strain gauge applications. To this purpose, polycarbonate substrates were irradiated at room temperature with low-energy metal ions (Cu⁺ and Ni⁺) and with fluences in the range between 1 × 10¹⁶ and 1 × 10¹⁷ ions/cm², in order to promote the precipitation of dispersed metal nanoparticles or the formation of a continuous thin film. The nanoparticle morphology and the microstructural properties of polymer nanocomposites were investigated by glancing-incidence X-ray diffraction and transmission electron microscopy (TEM) measurements. At lower fluences (<5 × 10¹⁶ ions/cm²) a spontaneous precipitation of spherical-shaped metal nanoparticles occurred below the polymer top-surface (∼50 nm), whereas at higher fluences the aggregation of metal nanoparticles produced the formation of a continuous polycrystalline nanofilm. Furthermore, a characteristic surface plasmon resonance peak was observed for nanocomposites produced at lower ion fluences, due to the presence of Cu nanoparticles. A reduced electrical resistance of the near-surface metal-polymer nanocomposite was measured. The variation of electrical conductivity as a function of the applied surface load was measured: we found a linear relationship and a very small hysteresis.     

Ion beam induced amorphization and recrystallization of Si/SiC/Si layer systems

Epitaxial, buried silicon carbide (SiC) layers have been fabricated in (100) and (111) silicon by ion beam synthesis (IBS). In order to study the ion beam induced epitaxial crystallization (IBIEC) of buried SiC layers, the resulting Si/SiC/Si layer systems were amorphized using 2 MeV Si²⁺ ion irradiation at 300 K. An unexpected high critical dose for the amorphization of the buried layers is observed. Buried, amorphous SiC layers were irradiated with 800 keV Si⁺ ions at 320 and 600°C, respectively, in order to achieve ion beam induced epitaxial crystallisation. It is demonstrated that IBIEC works well on buried layers and results in epitaxial recrystallization at considerably lower target temperatures than necessary for thermal annealing. The IBIEC process starts from both SiC/Si interfaces and may be accompanied by heterogenous nucleation of poly-SiC as well as interfacial layer-by-layer amorphization, depending on irradiation conditions. The structure of the recrystallized regions in dependence of dose, dose rate, temperature and crystal orientation is presented by means of TEM investigations.     

Ion source brightness and nuclear microprobe applications

The ion source used to provide beams for nuclear microprobe systems must ideally satisfy several demands. Of primary importance is the beam brightness. It is clearly desirable to employ the brightest possible source in order to focus the smallest possible probe size on the specimen, with the highest possible beam current. Also important is the need for minimal maintenance, particularly for ion sources used inside single ended accelerators.

We report here on measurements conducted on the beam from the RF ion source in our 5U Pelletron accelerator. We have found that the beam brightness is highly heterogenous, with the paraxial rays about an order of magnitude brighter than the surrounding rays. This is desirable for nuclear microprobe operation because probe forming lens systems optimised for large demagnification magnitude can exploit the high brightness of the paraxial region. We find several other accelerators around the world also exhibit this characteristic.     

Investigation of avalanche silicon detectors for low energy single ion implantation applications

Avalanche silicon photodiodes have potential applications to detect low energy single ions for counting single ion impacts in shallow implant depths for the deterministic doping of nanoscale electronic devices. This paper reports the investigation of avalanche photodiode detectors in the linear operation mode for detection of 0.5–2 MeV helium ions. The measured charge gain was found to be up to 100 depending on bias voltage. The charge gain was found to saturate at a level that correlated with the ion stopping depth in silicon. The measured charge gain for energetic ions, which have a well-defined depth in a silicon substrate for the deposition of ionization energy, is compared with that of X-rays and photons, which deposit the ionization energy over a wider range of depth. This allowed the identification of a suitable structure for an avalanche photodiode optimised for the detection of sub-10 keV heavy ions with an internal charge gain above 10 achievable. This offers significant advantages over conventional PIN devices where the signals from such ions would be lost in the noise.