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.

Magnetoconductivity of ten ZnO, Zn1−xCoxO, and Zn1−xMnxO thin films with nominal concentrations of 2.0 at.% and 0.1 at.% of Co2+ and Mn2+ ions, respectively, has been analyzed in the temperature range from 5 K to 200 K in in-plane and out-of-plane magnetic fields up to 6 T. The formation of a highly conducting surface layer can be controlled during thin film deposition, leading to a large variation of the sheet resistance, namely, from 2 × 103 Ω/◻ to 1 × 105 Ω/◻ at room temperature. Depending on the thickness of the highly conducting surface layer, a single two-dimensional (2D), a single three-dimensional (3D), or a two-dimensional and three-dimensional (2D + 3D) parallel conducting model was chosen to analyze the measured magnetoconductivity of the magnetic ZnO thin films with different electron spins (S=5/2 for Zn1−xMnxO and S=3/2 for Zn1−xCoxO) and with different Landé g-factors (isotropic for 3D Zn1−xMnxO and 2D Zn1−xCoxO and anisotropic for 2D Zn1−xMnxO and 3D Zn1−xCoxO).

Using two different types of impedance biochips (PS5 and BS5) with ring top electrodes, a distinct change of measured impedance has been detected after adding 1–5 µL (with dead or live Gram-positive Lysinibacillus sphaericus JG-A12 cells to 20 µL DI water inside the ring top electrode. We relate observed change of measured impedance to change of membrane potential of L. sphaericus JG-A12 cells. In contrast to impedance measurements, optical density (OD) measurements cannot be used to distinguish between dead and live cells. Dead L. sphaericus JG-A12 cells have been obtained by adding 0.02 mg/mL of the antibiotics tetracycline and 0.1 mg/mL chloramphenicol to a batch with OD0.5 and by incubation for 24 h, 30 °C, 120 rpm in the dark. For impedance measurements, we have used batches with a cell density of 25.5 × 108 cells/mL (OD8.5) and 270.0 × 108 cells/mL (OD90.0). The impedance biochip PS5 can be used to detect the more resistive and less capacitive live L. sphaericus JG-A12 cells. Also, the impedance biochip BS5 can be used to detect the less resistive and more capacitive dead L. sphaericus JG-A12 cells. An outlook on the application of the impedance biochips for high-throughput drug screening, e.g., against multi-drug-resistant Gram-positive bacteria, is given.