We present a comprehensive study of vacancy and vacancy-impurity complexes in InN combining positron annihilation spectroscopy and ab-initio calculations. Positron densities and annihilation characteristics of common vacancy-type defects are calculated using density functional theory and the feasibility of their experimental detection and distinction with positron annihilation methods is discussed. The computational results are compared to positron lifetime and conventional as well as coincidence Doppler broadening measurements of several representative InN samples. The particular dominant vacancy-type positron traps are identified and their characteristic positron lifetimes, Doppler ratio curves and lineshape parameters determined. We find that In vacancies and their complexes with N vacancies or impurities act as efficient positron traps, inducing distinct changes in the annihilation parameters compared to the InN lattice. Neutral or positively charged N vacancies and pure N vacancy complexes on the other hand do not trap positrons. The predominantly introduced positron trap in irradiated InN is identified as the isolated In vacancy, while in as-grown InN layers In vacancies do not occur isolated but complexed with one or more N vacancies. The number of N vacancies per In vacancy in these complexes is found to increase from the near surface region towards the layer-substrate interface.
Study of the optimal conditions for NV- center formation in type 1b diamond, using photoluminescence and positron annihilation spectroscopies
研究了质子辐照结合真空热退火在~1b型金刚石单晶中产生负电荷氮空位色心（NV-）的最佳工艺参数。几个样品在不同的辐照和退火条件下处理，其特征在于慢正电子束多普勒展宽和光致发光（PL）光谱。在高质子注量的另一个复杂的空位缺陷出现限制NV-的形成。根据PL测量，NV-的浓度估计高达2.3 x 10^18 cm^-3。此外，我们还用NV ~-理论推导了正电子的俘获系数。这项研究深入了解了金刚石中高浓度NV-的生产，这在超灵敏磁力测量和量子混合系统应用中至关重要。
Role of Se vacancies on Shubnikov de Haas oscillations in Bi2Se3: a combined magneto-resistance and positron annihilation study
磁电阻测量加上正电子寿命测量，以表征空位型缺陷，已进行了拓扑绝缘体（TI）系统Bi 2 Se 3，不同的Se/Bi的比例。在4 K至10 K温度范围内，在高达15 T的磁场中进行测量时，在标称Bi2Se3.1晶体中观察到明显的Shubnikov de Haas（SdH）振荡，磁场垂直于晶体的（001）平面。量子振荡，二维电子结构的特征，被认为只有在晶体中，具有较低浓度的硒空位，从正电子湮没光谱推断。
Split Ga vacancies and the unusually strong anisotropy of positron annihilation spectra in $\boldsymbolβ$-Ga$_2$O$_3$
本文报道了对$β$ $_2$ O $_3$晶格和Ga单空位缺陷中正电子湮没参数的系统的第一性原理研究，并补充了正电子-电子湮没的多普勒展宽的取向相关实验。我们发现$β$ -Ga $_2$ O $_3$晶格和所考虑的缺陷在它们的多普勒展宽信号中都表现出异常强的各向异性。该各向异性与$β$ $_2$ O $_3$晶体结构的低对称性相关，这导致即使在晶格中的离域状态下也不寻常的正电子一维约束.特别是，最近通过扫描透射电子显微镜观察到的分裂Ga空位产生异常各向异性的正电子湮没信号。我们发现在实验中，$β$ O $_3$样品中的正电子湮没信号似乎常常由分裂的Ga空位支配。
Challenges in predicting positron annihilation lifetimes in lead halide perovskites: correlation functionals and polymorphism
Université Paris-Saclay（巴黎萨克雷大学）；CEA（法国原子能和替代能源委员会）；Service de Recherches en Corrosion et Comportement des Matériaux, SRMP（腐蚀与材料行为研究服务，SRMP）；Department of Physics, IriG, Univ. Grenoble-Alpes and CEA（格勒诺布尔阿尔卑斯大学物理系，IriG 及 CEA）；CEA/DRF/IRAMIS；University Paris-Saclay（巴黎萨克雷大学）；Department of Physics, University of Helsinki（赫尔辛基大学物理系）
Modeling changes in atomic structure around a vacancy with increasing temperature and calculation of temperature dependences of vacancy characteristics in bcc iron
National Research Nuclear University MEPhI（莫斯科国立核能研究大学）；National Research Center "Kurchatov Institute"（库尔恰托夫国家研究中心）
Co-evolution of point defects and Cr-rich nano-phase in binary Fe-20 at.% Cr alloy: A comprehensive investigation using positron annihilation spectroscopy and atom probe tomography
