5 V, while for the point contacts in Figure 5c, the threshold voltage does not exceed 1 V. It is also noticed that there is a different response of the I-Vs in the two metal-dielectric-metal devices.
Figure 5 C -AFM measurements of a- TaN x . (a) Positive I-V curves (solid lines) of TaN x deposited on Au for four different points fitted by the space-charge-limited current (SCLC) model (dash lines). (b) Negative I-V curves (solid lines) of TaN x deposited on Au for the same points presented in (a) fitted by the SCLC LB-100 manufacturer model (dash lines). (c) Positive I-V curves of TaN x deposited on Si for three different points. The conductive part of the I-Vs exhibits an www.selleckchem.com/products/nu7026.html almost parabolic to almost ohmic behavior (d) Negative I-V curves of TaN x deposited on Si for the points presented
in (b). In all I-Vs, the leakage current is quite high, displaying also a very noisy profile. In general, the total current flowing PF-4708671 cell line through a semiconductor can be written as I tot = I b + I s, where I b is the current from the bulk part of the film and I s includes the electronic conduction through the surface states and through the space charge layer beneath the surface. Taking into account the amorphous nature of the semiconducting film, the main conduction mechanism from the bulk is expected to be the Poole-Frenkel effect [43]. Usually in amorphous materials, the predominant
conduction mechanism is the Poole-Frenkel effect, i.e., the thermal emission of electrons from charged vacancies, attributed to impurities and defects that are present in large numbers inside the bulk of the amorphous matrix [43, 44]. In the present samples, charged nitrogen vacancies act like Coulombic traps that promote the injection of electrons from the Au or Ag bottom electrode as the electric field increases during forward bias direction and from Pt/Ir tip during the reverse bias direction. For Poole-Frenkel emission, the current density is given by [45]: (1) where C and β are material dependent constants, E is the induced electric field, q is the electron charge, T is the temperature, k is the Boltzmann Obeticholic Acid constant, and φ is the ionization potential in V. The constant C is related to charge carrier mobility and trap’s density, while β is related to the dielectric constant ε 0 ε r via (2) Other possible charge carrier transport mechanisms from the bulk of the film could be thermionic emission of charge carriers across the metal-dielectric interface or field emission by electron tunneling from the metal or charge traps to the quasi-conduction band of the amorphous semiconductor [46]. These mechanisms have also exponential like I-V behavior.