NOA61 photopolymer as an interface for Al/NOA61/p-Si/Al heterojunction MPS device

The effect of the NOA61 photopolymer organic interlayer on the electrical and dielectric properties of the Al/NOA61/p-Si/Al metal-polymer-semiconductor (MPS) device has been reported the first time. The device parameters of the device such as rectification ratio (RR), ideality factor (n), and barrier height (Φ_B) were determined from the current–voltage (I–V) measurements according to thermionic emission theory (TE). Series resistance, R_S, values were also calculated by Norde and Cheung methods in the range of 2.4–3 kΩ. According to the reverse bias I–V measurements, the current was governed by Frenkel–Poole Emission (FPE) in the entire region. The voltage-dependent capacitance (C) and the conductance (G/ω) measurements were investigated at particular frequencies between 20 kHz and 1 MHz. The dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), and the complex electric modulus (M) were calculated using the measured C and G parameters, and it was seen that the interface states and surface dipoles at the interfacial layer were effective in the behavior of the device in alternating current. Additionally, the morphological properties of the thin film were studied by scanning electron microscopy (SEM). We observed that (NOA61) organic interlayer may be a noticeable alternative to a variety of electronic applications.

     

Thermotropic and Thermo-optical Properties of Nematic Mesophase at Direct and Reverse Phase Transitions

Comparative investigations of the thermo-optical, thermotropic, and thermo-morphologic properties of aligned and non-aligned textures in the nematic mesophase over a large temperature interval and in regions of direct and reverse phase transitions between the nematic mesophase and the isotropic liquid have been carried out. The character of the optical transmission and adsorption coefficient has been compared with that of the texture transformations. Nonlinearity of the thermo-optical and thermotropic behavior at the nematic mesophase–isotropic liquid and isotropic liquid–nematic mesophase phase transitions has been observed. Differences in the temperatures of phase transitions for the aligned and non-aligned textures of the nematic liquid crystals have been found.     

Temperature Dependent Current Transport Mechanism of Photopolymer Based Al/NOA60/p-Si MPS Device

A photopolymer based Al/Norland Optical Adhesive 60 (NOA60)/p-Si MPS (metal-polymer-semiconductor) device was fabricated by a combination of vacuum evaporation and smear technique. The current transport properties of the device were investigated by using the forward bias current–voltage (I-V) characteristic in the temperature range of 80–300 K. The cross-sectional structure of polymer/semiconductor was revealed by the scanning electron microscope (SEM) image and it was seen that the NOA60 photopolymer was tidily coated on the p-Si surface. According to the I-V measurements at room temperature, the MPS device exhibits a good rectification ratio of 8140 at?±?1 V. The temperature-dependent I-V measurements (I-V-T) were analyzed based on the thermionic emission (TE) theory and an abnormal increase in zero-bias barrier height (BH) and a decrease in ideality factor (n) was observed with increasing temperature. Additionally, two different linear regions with distinct values from the theoretical value of the Richardson constant (A*) were observed in the conventional Richardson plot. Such deviations from the ideal TE theory have been attributed to the effect of BH inhomogeneities. Gaussian distribution (GD) of the BH model has applied the I-V-T results and the double GD BH with mean values of 0.75?±?0.08 eV (80–140 K) and 1.02?±?0.11 eV (140–300 K) were calculated. Moreover, the A* value of 31.4 A/cm²K² was calculated close to the known value of p-Si from the modified Richardson plot. Thus, it has been concluded that the current transport of the Al/NOA60/p-Si MPS device can be explained by TE with a double GD BH model for a wide temperature region.