Limits...
Probing Defects in Nitrogen-Doped Cu 2 O

View Article: PubMed Central - PubMed

ABSTRACT

Nitrogen doping is a promising method of engineering the electronic structure of a metal oxide to modify its optical and electrical properties; however, the doping effect strongly depends on the types of defects introduced. Herein, we report a comparative study of nitrogen-doping-induced defects in Cu2O. Even in the lightly doped samples, a considerable number of nitrogen interstitials (Ni) formed, accompanied by nitrogen substitutions (NO) and oxygen vacancies (VO). In the course of high-temperature annealing, these Ni atoms interacted with VO, resulting in an increase in NO and decreases in Ni and VO. The properties of the annealed sample were significantly modified as a result. Our results suggest that Ni is a significant defect type in nitrogen-doped Cu2O.

No MeSH data available.


Hole density, hole mobility, and resistivity of (a) Cu2O:N samples annealed at 750°C as functions of the nitrogen plasma power (a power of 0 W represents an undoped sample) and (b) Cu2O:N samples doped with a nitrogen plasma power of 200 W as functions of the annealing temperature.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5384195&req=5

f2: Hole density, hole mobility, and resistivity of (a) Cu2O:N samples annealed at 750°C as functions of the nitrogen plasma power (a power of 0 W represents an undoped sample) and (b) Cu2O:N samples doped with a nitrogen plasma power of 200 W as functions of the annealing temperature.

Mentions: Figure 2(a) shows room temperature values for the hole density, mobility and resistivity of the Cu2O and Cu2O:N samples after annealing at 750°C for 10 min as functions of the nitrogen plasma power. A power of 0 W represents undoped Cu2O. It is clear that the hole density increased with the power of the nitrogen plasma (likely to be proportional to the doping level) and the mobilities of Cu2O:N were all smaller than those of Cu2O (also consistent with the hypothesis of high nitrogen incorporation). The hole concentrations of Cu2O:N were in the range of 1016 cm−3, i.e. two orders of magnitude higher than that of Cu2O12171819. Figure 2(b) presents the room temperature Hall data for Cu2O:N synthesized using nitrogen plasma power of 200 W, as a function of annealing temperature. The lowest resistivity and the highest hole density were obtained upon annealing at 750°C. When the sample was annealed at 800°C, although the mobility was higher because of the improved crystal quality, the hole density decreased, leading to reduced conductivity. A possible explanation is that annealing at such a high temperature may also induce the out diffusion of nitrogen in addition to the acceptor activation. Note that the annealing conditions can be further optimized for better conductivity; nevertheless, in our study, the results indicated that the samples annealed at 750°C were already suitable for the study of nitrogen-related defects on behalf of the prominent evolution in electrical properties. Furthermore, the temperature-dependent hole concentration was also measured to determine the activation energy of the dominant acceptors in Cu2O:N, which was calculated to be 121 meV (supplementary information). This level is attributed to extrinsic NO acceptors, because the only reasonable alternative of copper vacancies (VCu) exhibits a much deeper level212223. Figure 3 presents the nitrogen concentration versus depth profiles of the Cu2O:N films doped with 200 W nitrogen plasma as measured by secondary ion mass spectroscopy (SIMS), which confirms: (i) nitrogen incorporation into our films and (ii) its gradual out diffusion during anneals.


Probing Defects in Nitrogen-Doped Cu 2 O
Hole density, hole mobility, and resistivity of (a) Cu2O:N samples annealed at 750°C as functions of the nitrogen plasma power (a power of 0 W represents an undoped sample) and (b) Cu2O:N samples doped with a nitrogen plasma power of 200 W as functions of the annealing temperature.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384195&req=5

f2: Hole density, hole mobility, and resistivity of (a) Cu2O:N samples annealed at 750°C as functions of the nitrogen plasma power (a power of 0 W represents an undoped sample) and (b) Cu2O:N samples doped with a nitrogen plasma power of 200 W as functions of the annealing temperature.
Mentions: Figure 2(a) shows room temperature values for the hole density, mobility and resistivity of the Cu2O and Cu2O:N samples after annealing at 750°C for 10 min as functions of the nitrogen plasma power. A power of 0 W represents undoped Cu2O. It is clear that the hole density increased with the power of the nitrogen plasma (likely to be proportional to the doping level) and the mobilities of Cu2O:N were all smaller than those of Cu2O (also consistent with the hypothesis of high nitrogen incorporation). The hole concentrations of Cu2O:N were in the range of 1016 cm−3, i.e. two orders of magnitude higher than that of Cu2O12171819. Figure 2(b) presents the room temperature Hall data for Cu2O:N synthesized using nitrogen plasma power of 200 W, as a function of annealing temperature. The lowest resistivity and the highest hole density were obtained upon annealing at 750°C. When the sample was annealed at 800°C, although the mobility was higher because of the improved crystal quality, the hole density decreased, leading to reduced conductivity. A possible explanation is that annealing at such a high temperature may also induce the out diffusion of nitrogen in addition to the acceptor activation. Note that the annealing conditions can be further optimized for better conductivity; nevertheless, in our study, the results indicated that the samples annealed at 750°C were already suitable for the study of nitrogen-related defects on behalf of the prominent evolution in electrical properties. Furthermore, the temperature-dependent hole concentration was also measured to determine the activation energy of the dominant acceptors in Cu2O:N, which was calculated to be 121 meV (supplementary information). This level is attributed to extrinsic NO acceptors, because the only reasonable alternative of copper vacancies (VCu) exhibits a much deeper level212223. Figure 3 presents the nitrogen concentration versus depth profiles of the Cu2O:N films doped with 200 W nitrogen plasma as measured by secondary ion mass spectroscopy (SIMS), which confirms: (i) nitrogen incorporation into our films and (ii) its gradual out diffusion during anneals.

View Article: PubMed Central - PubMed

ABSTRACT

Nitrogen doping is a promising method of engineering the electronic structure of a metal oxide to modify its optical and electrical properties; however, the doping effect strongly depends on the types of defects introduced. Herein, we report a comparative study of nitrogen-doping-induced defects in Cu2O. Even in the lightly doped samples, a considerable number of nitrogen interstitials (Ni) formed, accompanied by nitrogen substitutions (NO) and oxygen vacancies (VO). In the course of high-temperature annealing, these Ni atoms interacted with VO, resulting in an increase in NO and decreases in Ni and VO. The properties of the annealed sample were significantly modified as a result. Our results suggest that Ni is a significant defect type in nitrogen-doped Cu2O.

No MeSH data available.