Strong Affinity between In and Al ImpuritiesDoped in ZnO
Strong Affinity between In and Al ImpuritiesDoped in ZnO
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ZnO 中掺杂的 In 和 Al 杂质之间具有强亲和力
DOI：
10.1143/jpsj.80.095001
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
andY. Ohkubo
中科院分区：
文献类型：
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作者：
S. Komatsuda;W. Sato;S. Kawata;andY. Ohkubo
近年来，掺杂第13族元素（Al、Ga、In）作为杂质施主的氧化锌（ZnO）被强烈期望应用于n型II-VI化合物半导体的功能器件中。已知半导体的电导率根据杂质的类型、浓度和引入方法而显着变化。 1）因此，为了精确控制电导率，有必要研究杂质的物理和化学状态。 2-4) 对于稀杂质附近电磁场的研究，采用放射性探针的核技术由于其高灵敏度而非常适合。利用这一优势，我们将时间微分扰动角相关（TDPAC）方法应用于ZnO中供体位点的局部场研究，采用从111 In分解的111 Cd（以下符号为111 Cdð 111 InÞ）作为核探针，期望111 In作为供体杂质的行为。在我们之前的TDPAC研究中，我们发现掺杂稀In、Ga和Al离子的ZnO中探针核处的局部场与未掺杂的ZnO明显不同。 5–7) 特别是对于 Al 掺杂的 ZnO，即使 Al 浓度低至 0.05 at.%(500ppm)，对 111 Cdð 111 InÞ 探针的掺杂效果也很突出。 7) 这一观察结果表明，由于 111 Cdð 111 InÞ 探针和 Al 离子在 ZnO 中热扩散，其局部关联的可能性很高。将我们的兴趣引向它们关联的概率，我们研究了可以观察到上面假设的它们关联的铝浓度的稀释极限。本文通过实验证明 111 Cdð 111 InÞ 探针可以与极稀的 Al 离子局部关联，证明了 ZnO 基质中 In 和 Al 离子之间存在强大的吸引力。根据我们之前的工作，通过固相反应分别合成了掺杂不同浓度铝的氧化锌样品。 6) 对于合成样品，我们从粉末 X 射线衍射图发现，即使对于 5000 ppm at.% Al 掺杂的 ZnO，晶格常数与纯 ZnO 相比也没有变化，并且没有检测到新相。 7) 对每个样品中掺杂浓度为 100 ppt 的 111 Cdð 111 InÞ 探针在级联射线上进行 TDPAC 测量，中间态为 I 1/4 5= 2，半衰期为 85.0 ns。 8) 在目前的工作中，对 TDPAC 进行了观察，以了解方向各向异性 A22G22ðtÞ，作为级联射线发射之间的时间间隔 t 的函数，在此期间探头受到外部周围场的扰动。这里，A22 表示仅取决于核特性的角度相关系数，G22ðtÞ 是时间微分扰动因子。
In recent years, zinc oxide (ZnO) doped with group 13 elements (Al, Ga, In) as impurity donors is strongly expected for application to functional devices as n-type II–VI compound semiconductors. It is known that the electric conductivity of the semiconductor drastically changes depending on the type, concentration, and introduction methods of impurities. 1) For the precise control of conductivity, therefore, it is essential to investigate the physical and chemical states of the impurities. 2–4) With respect to the study of the electromagnetic field in the vicinity of dilute impurities, nuclear techniques with radioactive probes are very suited because of their high sensitivity. Taking this advantage, we have applied the timedifferential perturbed angular correlation (TDPAC) method to the investigation of local fields at donor sites in ZnO, employing 111 Cd disintegrated from 111 In, symbolized as 111 Cdð 111 InÞ hereafter, as the nuclear probe expecting the behavior of 111 In as a donor impurity. In our previous TDPAC studies, we found that local fields at the probe nucleus in ZnO doped with dilute In, Ga and Al ions are distinctly different from that for undoped ZnO. 5–7) Especially for the Al-doped ZnO, in addition, the doping effect on the 111 Cdð 111 InÞ probe is prominent even at as low Al concentration as 0.05 at.%(500ppm). 7) This observation implies a high probability for the local association of the 111 Cdð 111 InÞ probe and Al ion (s) as a result of their thermal diffusion in ZnO. Directing our interest to the probability of their association, we investigated the dilute limit of Al concentration at which their association presumed above can be observed. The present paper proves the presence of a strong attractive force between In and Al ion (s) in ZnO matrix by showing an experimental evidence that the 111 Cdð 111 InÞ probe can be locally associated with extremely dilute Al ion (s). Zinc oxide samples doped with various Al concentrations were separately synthesized by a solid-state reaction following our previous work. 6) For the synthesized samples, we found from powder X-ray diffraction patterns that the lattice constants were unchanged from pure ZnO even for the 5000 ppm at.% Al-doped ZnO and new phases were not detected. 7) TDPAC measurements were performed for the 111 Cdð 111 InÞ probe doped in each sample at the concentration of 100 ppt on the cascade rays with the intermediate state of I ¼ 5= 2 having a half-life of 85.0 ns. 8) In the present work, observation of TDPAC was made for the directional anisotropy, A22G22ðtÞ, as a function of the time interval between the cascade-ray emissions, t, during which the probe is perturbed by the outer surrounding field. Here, A22 denotes the angular correlation coefficient depending only on the nuclear properties and G22ðtÞ is the time-differential perturbation factor.