采用离子注入法及退火工艺,在硅基二氧化硅薄膜中制备了镶嵌结构的天然Ge纳米晶样品.通过退火实验研究,发现随着退火温度的升高,纳米晶的晶态峰峰位红移,这意味着Ge纳米晶受到的应力减小.当退火温度达到700℃时,纳米晶的晶态峰强度显著增强,而且薄膜中与Ge有关的缺陷发光减弱.采用中子嬗变掺杂法对天然Ge纳米晶进行了掺杂,X射线荧光光谱数据表明,样品中成功的引入了Ga杂质和As杂质.薄膜中形成的与Ge有关的缺陷具有稳定的结构,中子辐照之后其发光仍然存在,而且,掺杂后的样品中没有发现与Ga或As有关的缺陷发光.

通过离子注入及中子嬗变掺杂制备了Ga(镓)掺杂70Ge(锗)纳米晶,并对样品进行了质子激发X射线荧光分析谱(PIXE)、光致发光谱(PL)、激光拉曼散射谱(LRS)的测量与研究.结果表明:随着Ga杂质浓度的增加,580 nm附近的荧光峰的发光强度不断地下降,这可能是非辐射的俄歇复合过程与纳米晶数量的减少共同作用的结果.此外,从PL上面看到580 nm附近的荧光峰蓝移则可能是由纳米晶尺寸的减小和非辐射的俄歇复合过程引起的.

Arsenic-doped isotopic Ge-74 nanocrystals (nc-Ge-74) embedded in amorphous SiO2 films were prepared by neutron transmutation doping (NTD) and the influence of the As additive on the optical properties of the samples was investigated. The optical results showed that the original nc-Ge-74 photoluminescence (PL) (similar to 620 nm) blue-shift and PL quenching could be seen by the appearance of Auger-like recombination channels, while the increase in PL was produced by neutron irradiation and a second annealing, not by the As impurities. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Isotope 74Ge ion implantation and neutron transmutation doping methods were carried out to prepare donor impurities (arsenic) doped Ge nanocrystals embedded in amorphous SiO2 film. The isotope 74Ge atoms can react with thermal neutron and transmute to 75As atoms, acting as donor impurities in Ge crystal. The photoluminescence intensity of donor doped Ge nanocrystals is observed increased first then decreased with increase of arsenic concentration. The non-monotonic dependence of photoluminescence on the level of doping is explained by following model: at low donor concentration, donor electrons can passivate non-radiative centers, as increasing the radiative efficiency; at high arsenic concentration, donor electrons remain free and reduce the radiative efficiency due to appearance of auger-like recombination channel.

Samples of Ge nanocrystals (Ge-ncs) embedded in amorphous SiO2 film were prepared by Ge ion implantation and subsequent primary thermal annealing. These samples were irradiated by neutron flux in a nuclear reactor followed by the second annealing. Irradiation with thermal neutrons leads to doping of nanocrystals with Ga, As and Se impurities due to nuclear transmutation of isotope Ge-70 into Ga-71, isotope 74 Ge into 75 As, isotope 76 Ge into 77 Se, respectively (neutron transmutation doping, NTD). Irradiation with fast neutrons leads to appearance of radiation damages, which are expected to be removed after the second annealing. Photoluminescence (PL) measurements show that PL is quenched after neutron irradiation, and restored after annealing higher than 500 degrees C. The PL spectra of doped Ge-nes samples show more intense exciton radiative luminescence than of undoped Ge-ncs sample, which is related to that the donor and acceptor impurities recombine the nonradiative centers in the interface of Ge-ncs and SiO2 matrix, and enhance the probability of exciton recombination. (c) 2007 Elsevier B.V. All rights reserved.