Substitutional replacement of N with O in epitaxial CrN(001) layers is achieved by reactive sputter deposition in a mixed ${\mathrm{N}}_2$ and $\mathrm{Ar}+{\mathrm{O}}_2$ atmosphere. O incorporation facilitates Cr vacancies, yielding a rocksalt-structure solid solution ${\mathrm{Cr}}_{1-x/2}{\mathrm{N}}_{1-x}{\mathrm{O}}_x$ with a single compositional parameter $x$ and a measured lattice constant that decreases from $a=0.4175$ to 0.4116 nm for $x=0$ to 0.59. First-principles calculations predict $da/dx=+0.0200$, −0.0018, and −0.0087 nm for $\mathrm{Cr}{\mathrm{N}}_{1-x}{\mathrm{O}}_x, {\mathrm{Cr}}_{1-x/3}{\mathrm{N}}_{1-x}{\mathrm{O}}_x$, and ${\mathrm{Cr}}_{1-x/2}{\mathrm{N}}_{1-x}{\mathrm{O}}_x$, respectively, and confirm, in combination with ion-beam compositional analyses and x-ray diffraction results, a vacancy concentration of $x/2$ per cation site. The room-temperature resistivity decreases by over two orders of magnitudes from $\rho =1.5\times {10}^{-3}$ to $7.7\times {10}^{-6}\mathrm{\Omega }\mathrm{m}$ for $x=0–0.26$. This is accompanied by a transition from a negative to a positive temperature coefficient of resistivity, an increase in the Hall mobility from ${\mu }_{\mathrm{H}}=0.37$ to $1.7{\mathrm{cm}}^2/\mathrm{Vs}$, an increase in the carrier concentration $n=1.1\times {10}^{20}$ to $4.9\times {10}^{21}{\mathrm{cm}}^{-3}$, and a decrease in the calculated band gap from 0.54 to 0 eV. However, $\rho$ increases again to $6.9\times {10}^{-5}\mathrm{\Omega }\mathrm{m}$ for $x=0.34$ and to $>10\mathrm{\Omega }\mathrm{m}$ for $x\ge 0.59$, with a corresponding drop in ${\mu }_{\mathrm{H}}$ and the opening of a gap. The maximum in the measured carrier density and conductivity at $x=0.26$ 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 $x=0.25\pm 0.05$. The measurements indicate insulator-to-metal and subsequent metal-to-insulator transitions at $x=0.04\pm 0.03$ and $0.30\pm 0.03$, respectively. The transition to metallic conduction is attributed to substitutional O on anion sites acting as donors, while the measured $n$ for $x=0.01–0.26$ quantitatively indicates charge compensation by cation vacancies that act as acceptors. The insulating properties at large $x$ are likely caused by increased electron correlation effects.

中文翻译：

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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 ${\mathrm{ñ}}_2$ 和 $\mathrm{氩气}+{\mathrm{Ø}}_2$大气层。O的掺入促进Cr的空位，产生岩石盐结构的固溶体${铬}_{\mathrm{1个}-X/2}{\mathrm{ñ}}_{\mathrm{1个}-X}{\mathrm{Ø}}_X$ 具有单个成分参数 $X$ 和测量的晶格常数从 $\mathrm{一种}=0.4175$ 到0.4116 nm $X=0$至0.59。第一性原理计算预测$d\mathrm{一种}/dX=+0.0200$，-0.0018和-0.0087 nm $铬{\mathrm{ñ}}_{\mathrm{1个}-X}{\mathrm{Ø}}_X， {铬}_{\mathrm{1个}-X/3}{\mathrm{ñ}}_{\mathrm{1个}-X}{\mathrm{Ø}}_X$和 ${铬}_{\mathrm{1个}-X/2}{\mathrm{ñ}}_{\mathrm{1个}-X}{\mathrm{Ø}}_X$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 $X/2$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$\rho =1.5\times {10}^{-3}$ 至 $7.7\times {10}^{-6}\mathrm{\Omega }\mathrm{米}$ 对于 $X=0–0.26$。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${\mu }_{\mathrm{H}}=0.37$ 至 $1.7{\mathrm{厘米}}^2/\mathrm{VS}$，载流子浓度增加 $ñ=1.1\times {10}^{20}$ 至 $4.9\times {10}^{21}{\mathrm{厘米}}^{-3}$，并将计算出的带隙从0.54降低到0 eV。然而，$\rho$ 再次增加到 $6.9\times {10}^{-5}\mathrm{\Omega }\mathrm{米}$ 对于 $X=0.34$ 并 $>10\mathrm{\Omega }\mathrm{米}$ 对于 $X\ge 0.59$，相应的下降 ${\mu }_{\mathrm{H}}$和差距的扩大。测得的载流子密度和电导率中的最大值$X=0.26$ 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 $X=0.25\pm 0.05$。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$X=0.04\pm 0.03$ 和 $0.30\pm 0.03$， 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$ñ$ 对于 $X=0.01–0.26$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$X$ 可能是由于电子相关效应增加所致。