Increased static dielectric constant in ZnMnO and ZnCoO thin films with bound magnetic polarons

Abstract

A novel small signal equivalent circuit model is proposed in the inversion regime of metal/(ZnO, ZnMnO, and ZnCoO) semiconductor/Si 3 N 4 insulator/p-Si semiconductor (MSIS) structures to describe the distinctive nonlinear frequency dependent capacitance (C-F) and conductance (G-F) behaviour in the frequency range from 50 Hz to 1 MHz. We modelled the fully depleted ZnO thin films to extract the static dielectric constant (ε r) of ZnO, ZnMnO, and ZnCoO. The extracted enhancement of static dielectric constant in magnetic n-type conducting ZnCoO (ε r ≥ 13.0) and ZnMnO (ε r ≥ 25.8) in comparison to unmagnetic ZnO (ε r = 8.3-9.3) is related to the electrical polarizability of donor-type bound magnetic polarons (BMP) in the several hundred GHz range (120 GHz for CdMnTe). The formation of donor-BMP is enabled in n-type conducting, magnetic ZnO by the s-d exchange interaction between the electron spin of positively charged oxygen vacancies V o + in the BMP center and the electron spins of substitutional Mn 2+ and co 2+ ions in ZnMnO and ZnCoO, respectively. The BMP radius scales with the Bohr radius which is proportional to the static dielectric constant. Here we show how BMP overlap can be realized in magnetic n-ZnO by increasing its static dielectric constant and guide researchers in the field of transparent spintronics towards ferromagnetism in magnetic, n-ZnO.

Doping Nature of Group V Elements in ZnO Single Crystals Grown from Melts at High Pressure

“…Note that expression gives a reasonable estimate for A 1 (TO) peak position k 0 = 358 cm –1 in ZnO. For this estimate, we took the Millikan charge calculated for ZnO clusters q = 0.9 e ( e is the elementary charge), ε ∞ = n 0 2 = 4 ( n 0 is the refractive index), and ε = 8.6 . This shows the applicability of the simplified expression for the A 1 (TO) mode.…”

“…For this estimate, we took the Millikan charge calculated for ZnO clusters q = 0.9e (e is the elementary charge), 45 ε ∞ = n 0 2 = 4 (n 0 is the refractive index), 46 and ε = 8.6. 47 This shows the applicability of the simplified expression 2 for the A 1 (TO) mode. Suppose that dielectric permittivity is independent on ion concentration in the static and high-frequency limits.…”

Magneto-Optical and Muliferroic Properties of Transition-Metal (Fe, Co, or Ni)-Doped ZnO Layers Deposited by ALD

“…From this point of view, the formation of NiO clusters in the ZnO matrix, which was suggested to occur in similar layers with lower Ni doping, is a possible explanation for the increased ε r at f = 10 3 –10 4 Hz. It should be noted that the calculated static dielectric constant ε r of Fe- and Ni-doped ZnO layers is significantly larger than that of the host ZnO, which is usually reported to be ε r = 8–9 . Recently, Vegesna et al attributed the increase of the static dielectric constant in magnetic n-type Co- and Mn-doped ZnO layers to the contribution of BMPs to the electrical polarization.…”

“…It should be noted that the calculated static dielectric constant ε r of Fe- and Ni-doped ZnO layers is significantly larger than that of the host ZnO, which is usually reported to be ε r = 8–9. 51 Recently, Vegesna et al 51 attributed the increase of the static dielectric constant in magnetic n-type Co- and Mn-doped ZnO layers to the contribution of BMPs to the electrical polarization. These polarons are formed by s–d exchange interaction between electron spins of the positively charged oxygen vacancy V o + in the BMP center and the electron spins of substitutional dopant ions.…”

Improved Electron Transport Properties of Zn-Rich In–Ga–Zn–O Thin-Film Transistors

“…According to the Poisson equation, the carrier accumulation layer becomes thick when the dielectric permittivity of the semiconductor is large, or the residual carrier concentration is high. The dielectric constant of amorphous InGaZnO 4 is 16, and that of ZnO is ∼9 . Therefore, it is impossible to explain why the effective thickness of IGZO m increases with m using the dielectric constant scenario.…”