中子辐照硅的正电子湮没研究

采用正电子湮没方法研究了１．４５×１０＾２０ｎ／ｃｍ＾２和３．１０×１０＾１７ｎ／ｃｍ＾２快中子辐照高纯单晶硅的辐射损伤及其退火效应。在３４３－１０７３Ｋ温度范围内测量了正电子湮没寿命随退火温度的变化。实验观察到氧－空位对和在高中子剂量辐照的Ｓｉ中发现的双空位复合成四空位。正电子湮没短寿命成分τ１是晶格正电子寿命和氧－空位对捕获的正电子寿命的加权平均值，而长寿命成分τ２是双空位或四空位捕获的正电子     

5.0MeV和9.5MeV快中子辐照在GaAs中产生的辐射损伤的正电子湮没研究

采用正电子湮没寿命测量方法研究了５．０ＭｅＶ和９．５ＭｅＶ快中子辐照在ＧａＡｓ中产生的辐射损伤，实验结果表明１０＾１１－１０＾１２ｎ／ｃｍ＾２注量的中子辐照只产生单空位缺陷１０＾１３ｎ／ｃｍ＾３注量的中子辐照产生单空位和双空位缺陷，１０＾１２ｎ／ｃｍ＾２注量的９．５ＭｅＶ中子辐照的ＧａＡｓ经４５０－６２０℃退火产生三空位缺陷，产生的缺陷浓度随中子能量和注量的增大而增大，但缺陷产生率对中子注量更灵敏     

裂变快中子辐照在GaAs中产生缺陷的正电子湮没研究

采用自电子湮没寿命测量方法研究了注量为６．５×１０＾１５／ｃｍ＾２和１．４×１０＾１４／ｃｍ＾２，Ｅｎ≥１ＭｅＶ的裂变中子辐照在掺Ｓｉ，Ｎ型单晶ＧａＡｓ产物的缺陷，此辐照在ＧａＡｓ中产生单空位和双空位缺限，缺陷浓度于比于辐照注量，高温退火产生三空位缺陷及小空位团，单空位，双空位和三空位缺陷的退火温度分别为２５０，４５０，６５０℃。     

高纯硅辐射损伤的正电子湮没和扰动角关联研究

采用正电子湮没和扰动角关联方法研究了１．４５×１０２０、３．１０×１０１７ｎ／ｃｍ２中子辐照和５×１０１１／ｃｍ２１７８Ｗ重离子辐照单晶硅引起的辐射损伤及其退火效应。实验测量的正电子湮没寿命和四极相互作用频率表明在Ｓｉ中存在氧一单空位对．高中子剂量和重离子辐照Ｓｉ后，用两种方法都观察到了双空位复合成四空位。     

85 MeV19F离子辐照InP正电子湮没研究

用正电子湮没寿命技术研究了注量为１．６＊１０＾１６ＣＭ＾－２Ｒ ８５ＭｅＶ＾１９Ｆ离子辐照ＩｎＰ产生的辐照效应。实验表明辐照在ＩｎＰ中产生单空位型缺陷。     

高注量快中子辐照在α—Al2O3中产生空洞的正电子湮没研究

采用正电子湮没技术研究３×１０＾２０／ｃｍ＾２中子注量，Ｅｎ≥１ＭｅＶ快中子辐照在α－Ａｌ２Ｏ３中产生的辐照效应，实验发现α－Ａｌ２Ｏ３在辐照后的８５０℃退火形成尺寸约为０．７ｎｍ的空洞。     

中子辐照注量对单晶硅中缺陷退火行为的影响

用正电子湮没寿命和多普勒加宽测量研究了不同注量中子辐照的氩气氛区熔单晶硅中缺陷的退火行为，发现不同中子注量辐照时，辐照致空位型缺陷的退火行为十分类似，并均在５５０℃时退火消除；但辐照致双空位浓度、二次双空位和四空位型缺陷的产生、浓度和消除温度很不相同。简单陷阱模型不适用于５００℃以下退火的离中子注量辐照的单晶硅，但能部分适用于中等注量辐照的单晶硅。     

热中子辐照提高掺硼YBaCuO超导体Jc的研究

掺杂天然硼的熔融织构生长（Ｍｅｌｔ－ｔｅｘｔｕｒｅｄＧｒｏｗｔｈ）的ＹＢｘＢａ２Ｃｕ３Ｏｙ（ｘ＝０．０１５,０．０３５）超导体经注量为５＊１０＾１７ｃｍ＾－２的热中子辐照后,磁临界电流密度Ｊｃ增至３．８倍。＾１０Ｂ（ｎ,α）＾Ｌｉ、＾７Ｌｉ＊（Ｑ＝＋２．７９ＭｅＶ）核反应出射的高能粒子能在超导体中产生均分布的,可以作为磁通钉扎中心的辐照伤,以便提高Ｊｃ。掺硼超导体热中子辐照后射性副产物的半衰期较短     

15MnTi钢的中子辐照效应

介绍了１５ＭｎＴｉ钢的母材，焊缝及其热影响区在不同注量的快中子辐照后，材料的机械性能变化的情况，根据试验结果表明，辐照温度为５０℃，快中子注量在１．０×１０＾１８ｃｍ＾－２到６．０×１０＾１８ｃｍ＾－２之间，１５ＭｎＴｉ钢的脆性转变温度增量△Ｔｃｖ与积分快中子注量的经验关系公式。     

高能（MeV级）氧离子注入本征型GaAs的电性能及注入损伤退火行为的研究

在本征型ＧａＡｓ中注入２．０ＭｅＶ（剂量１．０×１０＾１５／ｃｍ＾２）＋２．９ＭｅＶ（剂量１．１×１０＾１５／ｃｍ＾２）的＾１６Ｏ，使氧在约１．５－２．５μｍ之间形成均匀分布。注入样品分别经４００－８００℃、１５ｍｉｎ热退火后的电阻率测量表明，经５００℃和６００℃退火后的样品具有高的电阻率（～１０＾８Ω·ｃｍ）；而当退火温度进一步升高时，其电阻率逐渐下降，并具有ｐ型导电行为。沟道ＲＢＳ分析表明，当     

Radiation Effects on GaAs Charge Coupled Devices with High Resistivity Gate Structures

The results of a study on the effects of 1 MeV electrons and 1 MeV neutrons on the operation of high speed GaAs Charge Coupled Devices (CCDs) are presented. Radiation-induced trapping levels are characterized using a linear array CCD structure and the periodic pulse technique. 1 MeV electron irradiation introduced traps at 0.1 eV and 0.39 eV with bulk trap introduction rates of 1 cm-1 and 0.33 cm-1, respectively. The devices were irradiated to a maximum fluence of 9×1014 electrons/cm2. 1 MeV neutron irradiation introduced an electron trap level at 0.64 eV with a bulk trap introduction rate of 0.5 cm-1. Catastrophic device failure occurred at neutron fluences of 6×1013 neutrons/cm2. Device charge transfer efficiency was characterized pre- and post-irradiation over the temperature range of 80°K to 300°K.     

Ion-irradiation-induced athermal annealing of helium bubbles in SiC

We have compared the microstructural evolution of helium bubbles under ion irradiation and high temperature annealing. 4H-SiC was irradiated first by 140 keV He ions to a fluence of 1.0 × 10¹⁷ cm⁻² and then annealed at 1200 K for 30 min. Then, the samples were either irradiated by 2 MeV He ions to a fluence of 3.0 × 10¹⁶ cm⁻² at room temperature or annealed additionally at 1200 K for 30 min. Before and after 2 MeV He ion irradiation, significant microstructural changes were observed, similar to effects of high temperature annealing. Thus, the study provides evidence of ion-irradiation-induced athermal annealing on defect Ostwald ripening process and bubble evolution. Possible mechanisms are discussed.     

The energy dependence of proton-induced degradation in AlGaN/GaN high electron mobility transistors

The effects of proton irradiation at various energies are reported for AlGaN/GaN high electron mobility transistors (HEMTs). The devices exhibit little degradation when irradiated with 15-, 40-, and 105-MeV protons at fluences up to 10/sup 13/ cm/sup -2/, and the damage completely recovers after annealing at room temperature. For 1.8-MeV proton irradiation, the drain saturation current decreases 10.6% and the maximum transconductance decreases 6.1% at a fluence of 10/sup 12/ cm/sup -2/. The greater degradation measured at the lowest proton energy considered here is caused by the much larger nonionizing energy loss of the 1.8-MeV protons.     

Structural and optical properties of 6H-SiC helium-implanted at 600 K

Single crystals of 6H-SiC were implanted at 600 K with 100 keV He ions to three successively fluences and subsequently annealed at different temperatures ranging from 873 to 1473 K in vacuum. The recovery of lattice damage was investigated by different techniques including Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy and Fourier transform infrared spectroscopy. All three techniques showed that the damage induced by helium ion implantation in the lattice is closely related to the fluence. Rutherford backscattering spectrometry/channeling data on high temperature implantations suggest that for a fluence of 3 × 10¹⁶ He⁺/cm², extended defects are created by thermal annealing to 1473 K. Apart from a well-known intensity decrease of scattering peaks in Raman spectroscopy it was found that the absorbance peak in Fourier transform infrared spectroscopy due to the stretching vibration of Si-C bond shifted to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with increasing annealing temperature. These phenomena are attributed to different lattice damage behavior induced by the hot implantation process, in which simultaneous recovery was prevailing.     

高能氧离子注入LN晶体光波导的色心形成

采用高能氧离子注入同成分铌酸锂(LN)晶体中制备离子注入光波导,对制备的光波导进行(200°C–500°C)不同温度的退火处理。采用常规光谱法对退火后的光波导进行光吸收谱研究。研究发现,氧离子注入后会使LN晶体中的锂离子发生缺失,进一步偏离化学剂量比;随氧离子注入剂量的增加,锂离子缺失的现象会加重。研究还发现离子注入后样品的吸收强度增加,注入剂量增大,其光吸收强度也提高,说明经离子注入后产生的色心点缺陷数目随注入剂量而增加。研究表明,主要的吸收色心缺陷有氧空位、激化子、间隙原子缺陷及反位Nb离子捕获电子等缺陷,由于这些色心缺陷的共同作用,导致了氧离子注入LN晶体的光吸收强度的加强。在实验的退火温度范围内,这些色心缺陷消除程度不显著,在LN晶体采用氧离子注入形成的光波导具有优良的温度稳定性。     

Structural characterization of amorphous Fe–Si and its recrystallized layers

We have synthesized amorphous Fe–Si thin layers and investigated their microstructure using transmission electron microscopy (TEM). Si single crystals with (1 1 1) orientation were irradiated with 120 keV Fe⁺ ions to a fluence of 4.0 × 10¹⁷ cm⁻² at cryogenic temperature (120 K), followed by thermal annealing at 1073 K for 2 h. A continuous amorphous layer with a bilayered structure was formed on the topmost layer of the Si substrate in the as-implanted specimen: the upper layer was an amorphous Fe–Si, while the lower one was an amorphous Si. After annealing, the amorphous bilayer crystallized into a continuous β-FeSi₂ thin layer.     

离子辐照GaAs的光致发光和拉曼散射研究

利用250 keV质子和4.5 MeV氪离子(Kr17+)辐照未掺杂GaAs,注量分别为1×10~(12)-3×10~(14) cm~(-2)和3×10~(11)-3×10~(14) cm~(-2),使用光致发光谱和拉曼散射谱分析表征。发光谱的结果表明,随着剂量增大,质子辐照后的CAs峰及其声子伴线逐渐减弱,913 nm处的复合缺陷峰则先增大后减小,此峰与材料制备时的Cu掺杂无关。Kr离子辐照后本征发光峰则完全消失。拉曼散射谱的结果表明,相比于质子辐照,Kr离子辐照后LO声子峰峰位向低频方向移动,出现非对称性展宽,晶体结构发生明显改变。质子和Kr离子辐照效应的差异是由于移位损伤相差至少三个量级造成的。最后采用多级损伤累积(Multi-step damage accumulation,MSDA)模型得到了材料内缺陷的演化过程,并很好地解释了随损伤剂量增大GaAs光学性能及晶体结构的变化趋势。     

不同能量和注量电子辐照对InP HEMT材料电学特性影响

本文采用气态源分子束外延法(GSMBE)制备了匹配型InGaAs/InAlAs磷化铟基高电子迁移率器件(InP HEMT)外延结构材料。针对该外延结构材料开展了不同能量和注量电子束辐照试验,测试了InP HEMT外延结构材料二维电子气（2DEG）辐照前后的电学特性,获得了辐照前后InP HEMT外延材料二维电子气浓度和迁移率归一化退化规律,分析了不同能量和注量电子束辐照对外延材料电学特性的影响。结果发现：在相同辐照注量2×1015 cm-2条件下,电子束辐照能量越高,InP HEMT外延材料电学特性退化越严重;15 MeV电子束辐照时,当辐照注量超过4×1014 cm-2后,外延材料电学特性开始明显退化,当电子辐照注量达到3×1015 cm-2后,外延材料电学特性退化趋势减弱趋于饱和。产生上述现象原因如下：电子束与材料晶格发生能量传递,产生非电离能损(NIEL),破坏晶格完整性,高能量电子束具有较高的非电离能损,会产生更多的位移损伤缺陷,导致InP HEMT外延材料电学特性更严重退化;InP HEMT外延材料电学特性主要受沟道InGaAs/InAlAs异质界面能带结构和各种散射过程影响,随着电子辐照注量的增加,位移损伤剂量增大,辐射损伤诱导缺陷会在沟道异质界面处集聚直至饱和。     

Comparative study of damage production in ion implanted III–V-compounds at temperatures from 20 to 420 K

The damage evolution in ion implanted InP, GaAs, GaP and InAs is studied as a function of the ion fluence in the temperature range 20–420 K using various ion masses. It is shown that the macroscopic behaviour can be described in terms of critical temperatures T_c which depend on the ion mass and on the dose rate for a given material. At temperatures T_I< T_c amorphization is obtained by direct impact amorphization and the growing of the amorphous zones. However, athermal in-cascade annealing is observed even at 20 K, which is the more pronounced the lighter the ion is. This indicates the influence of the density of the primary cascades on defect recombination. Around T_c intrinsic defects are mobile leading to an equilibrium between defect production and annealing over a broad dose region. Amorphization at very large ion fluences is the consequence of complex processes which are influenced by the high ion concentration and the formation of dislocation bands near the end of range. Using an empirical formula which describes the ion mass and dose rate dependence of the critical temperature, the damage evolution for certain implantation conditions becomes predictable.     

Photoluminescence and photoluminescence excitation studies in 80 MeV Ni ion irradiated MOCVD grown GaN

We report damage creation and annihilation under energetic ion bombardment at a fixed fluence. MOCVD grown GaN thin films were irradiated with 80 MeV Ni ions at a fluence of 1 × 10¹³ ions/cm². Irradiated GaN thin films were subjected to rapid thermal annealing for 60 s in nitrogen atmosphere to anneal out the defects. The effects of defects on luminescence were explored with photoluminescence measurements. Room temperature photoluminescence spectra from pristine sample revealed presence of band to band transition besides unwanted yellow luminescence. Irradiated GaN does not show any band to band transition but there is a strong peak at 450 nm which is attributed to ion induced defect blue luminescence. However, irradiated and subsequently annealed samples show improved band to band transitions and a significant decrease in yellow luminescence intensity due to annihilation of defects which were created during irradiation. Irradiation induced effects on yellow and blue emissions are discussed.