Diode-Like Current Leakage and Ferroelectric Switching in Silicon SIS Structures with Hafnia-Alumina Nanolaminates

Silicon semiconductor-insulator-semiconductor (SIS) structures with high-k dielectrics are a promising new material for photonic and CMOS integrations. The “diode-like” currents through the symmetric atomic layer deposited (ALD) HfO2/Al2O3/HfO2… nanolayers with a highest rectification coefficient 103 are observed and explained by the asymmetry of the upper and lower heterointerfaces formed by bonding and ALD processes. As a result, different spatial charge regions (SCRs) are formed on both insulator sides. The lowest leakages are observed through the stacks, with total Al2O3 thickness values of 8–10 nm, which also provide a diffusive barrier for hydrogen. The dominant mechanism of electron transport through the built-in insulator at the weak field E < 1 MV/cm is thermionic emission. The Poole-Frenkel (PF) mechanism of emission from traps dominates at larger E values. The charge carriers mobility 100–120 cm2/(V s) and interface states (IFS) density 1.2 × 1011 cm−2 are obtained for the n-p SIS structures with insulator HfO2:Al2O3 (10:1) after rapid thermal annealing (RTA) at 800 °C. The drain current hysteresis of pseudo-metal-oxide-semiconductor field effect transistor (MOSFET) with the memory window 1.2–1.3 V at the gate voltage |Vg| < ±2.5 V is maintained in the RTA treatment at T = 800–900 °C for these transistors.

Nonlinear Optical Rectification in a Polar Molecule-Plasmonic Nanoparticle Structure

The study of nonlinear optical properties of quantum systems, such as quantum dots and molecules, near plasmonic nanostructures, has attracted significant interest in the past decade. Several nonlinear phenomena have been studied in quantum systems next to plasmonic nanostructures, such as second and third harmonic generations, Kerr nonlinearity, four-wave mixing, optical bistability, and nonlinear optical rectification. The latter occurs in asymmetric quantum systems and it can be strongly influenced, enhanced, or suppressed, depending on the particular plasmonic nanostructure used. In this work, we theoretically studied the nonlinear optical rectification of a polar two-level quantum system, a specific molecule, the zinc–phalocyanine molecular complex, interacting with an optical field near a gold nanoparticle. Initially, we used the steady-state solution of the density matrix equations for determining the correct form of the nonlinear optical rectification coefficient. We then used ab initio electronic structure calculations for determining the electronic structure of the molecule under study, i.e., the necessary energy differences and the induced and permanent electric dipole moments. We also used classical electromagnetic calculations for calculating the influence of the metallic nanoparticle on the decay rates of the molecule due to the Purcell effect and on the electric field applied in the molecule in the presence of the metallic nanoparticle. We then used the above to investigate the form of the corresponding nonlinear coefficient in the absence and presence of the plasmonic nanoparticle for various parameters. We found that the nonlinear optical rectification coefficient can be enhanced for specific field polarization and for suitable distance between the molecule and the plasmonic nanoparticle. Additionally, we observed that high efficiency of this process was obtained for weak field intensity, zero pure dephasing rates, and for small values of the transition dipole moments.

Room temperature I–V and C–V characteristics of Au/mTPP/p-Si organic MIS devices

The room temperature electrical characteristics of the organic Au/mTPP/p-Si device fabricated by spin coating method were investigated with I–V and C–V measurements. It has been determined that the device has a high rectification coefficient and current transport is dominated by the thermionic emission. The serial resistance value is calculated at 92 ohms with two different approaches. Serial resistance effects were also found to be effective in C–V and G–V measurements. The different barrier heights from the I–V and C–V measurements indicate possible interface and trap states or barrier inhomogeneities.