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Metal-insulator transitions in epitaxial rocksalt-structureCr1−x/2N1−xOx(001)
Physical Review B ( IF 3.2 ) Pub Date : 2020-12-01 , DOI: 10.1103/physrevb.102.235102 Mary E. McGahay , Sanjay V. Khare , Daniel Gall
Physical Review B ( IF 3.2 ) Pub Date : 2020-12-01 , DOI: 10.1103/physrevb.102.235102 Mary E. McGahay , Sanjay V. Khare , Daniel Gall
Substitutional replacement of N with O in epitaxial CrN(001) layers is achieved by reactive sputter deposition in a mixed and atmosphere. O incorporation facilitates Cr vacancies, yielding a rocksalt-structure solid solution with a single compositional parameter and a measured lattice constant that decreases from to 0.4116 nm for to 0.59. First-principles calculations predict , −0.0018, and −0.0087 nm for , and , respectively, and confirm, in combination with ion-beam compositional analyses and x-ray diffraction results, a vacancy concentration of per cation site. The room-temperature resistivity decreases by over two orders of magnitudes from to for . This is accompanied by a transition from a negative to a positive temperature coefficient of resistivity, an increase in the Hall mobility from to , an increase in the carrier concentration to , and a decrease in the calculated band gap from 0.54 to 0 eV. However, increases again to for and to for , with a corresponding drop in and the opening of a gap. The maximum in the measured carrier density and conductivity at is attributed to a maximum in the density of states near the Fermi level, in perfect agreement with calculations using supercells with randomly distributed O substitutions and Cr vacancies that predict a maximum at . The measurements indicate insulator-to-metal and subsequent metal-to-insulator transitions at and , respectively. The transition to metallic conduction is attributed to substitutional O on anion sites acting as donors, while the measured for quantitatively indicates charge compensation by cation vacancies that act as acceptors. The insulating properties at large are likely caused by increased electron correlation effects.
中文翻译:
外延岩盐结构中的金属-绝缘体过渡Cr1-x / 2N1-xOx(001)
外延CrN(001)层中的O用N取代N是通过在混合状态下进行反应溅射沉积来实现的 和 大气层。O的掺入促进Cr的空位,产生岩石盐结构的固溶体 具有单个成分参数 和测量的晶格常数从 到0.4116 nm 至0.59。第一性原理计算预测,-0.0018和-0.0087 nm 和 并结合离子束组成分析和X射线衍射结果确定空位浓度为 每个阳离子位点。室温下的电阻率相对于室温下降了两个数量级以上 至 对于 。这伴随着电阻率从负温度系数到正温度系数的跃迁,霍尔迁移率从 至 ,载流子浓度增加 至 ,并将计算出的带隙从0.54降低到0 eV。然而, 再次增加到 对于 并 对于 ,相应的下降 和差距的扩大。测得的载流子密度和电导率中的最大值 归因于费米能级附近的状态密度的最大值,这与使用具有随机分布的O取代和Cr空位的超级单元进行的计算完全吻合,而Cr空位预测了 。测量结果表明绝缘子到金属以及随后的金属到绝缘子的转变在 和 , 分别。向金属导电的过渡归因于阴离子位点上作为供体的取代O,而 对于 定量表示通过充当受体的阳离子空位进行的电荷补偿。绝缘性能大 可能是由于电子相关效应增加所致。
更新日期:2020-12-02
中文翻译:
外延岩盐结构中的金属-绝缘体过渡Cr1-x / 2N1-xOx(001)
外延CrN(001)层中的O用N取代N是通过在混合状态下进行反应溅射沉积来实现的 和 大气层。O的掺入促进Cr的空位,产生岩石盐结构的固溶体 具有单个成分参数 和测量的晶格常数从 到0.4116 nm 至0.59。第一性原理计算预测,-0.0018和-0.0087 nm 和 并结合离子束组成分析和X射线衍射结果确定空位浓度为 每个阳离子位点。室温下的电阻率相对于室温下降了两个数量级以上 至 对于 。这伴随着电阻率从负温度系数到正温度系数的跃迁,霍尔迁移率从 至 ,载流子浓度增加 至 ,并将计算出的带隙从0.54降低到0 eV。然而, 再次增加到 对于 并 对于 ,相应的下降 和差距的扩大。测得的载流子密度和电导率中的最大值 归因于费米能级附近的状态密度的最大值,这与使用具有随机分布的O取代和Cr空位的超级单元进行的计算完全吻合,而Cr空位预测了 。测量结果表明绝缘子到金属以及随后的金属到绝缘子的转变在 和 , 分别。向金属导电的过渡归因于阴离子位点上作为供体的取代O,而 对于 定量表示通过充当受体的阳离子空位进行的电荷补偿。绝缘性能大 可能是由于电子相关效应增加所致。