Space charge capacitance study of GaP/Si multilayer structure grown by plasma deposition

Microcrystalline GaP/Si multilayer structures grown on GaP substrates using combination of PE-ALD for GaP and PECVD for Si layers deposition are studied by three main space charge capacitance techniques: C-V profiling, admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS), which have been used on Schottky barriers formed on the GaP/Si multilayer structures. C-V profiling qualitatively demonstrates an electron accumulation in the Si/GaP wells. However, quantitative determination of the concentration and spatial position of its maximum is limited by the strong frequency dependence of the capacitance caused by electron capture/emission processes in/from the Si/GaP wells. These processes lead to signatures in AS and DLTS with activation energies equal to 0.39±0.05 eV and 0.28±0.05 eV, respectively, that are linked to the energy barrier at the GaP/Si interface. It is shown that the value obtained by AS (0.39±0.05 eV) is related to the response from Si/GaP wells located in the quasi-neutral region of the Schottky barrier, and it corresponds to the conduction band offset at the GaP/Si interface, while DLTS rather probes wells located in the space charge region closer to the Schottky interface where the internal electric field yields to a lowering of the effective barrier in the Si/GaP wells. Two additional signatures were detected by DLTS, which are identified as defect levels in GaP. The first one is associated to the SiGa+VP complex, while the second was already detected in single microcrystalline GaP layers grown by PE-ALD.

A Review: Ion Transport of Two-Dimensional Materials in Novel Technologies from Macro to Nanoscopic Perspectives

Ion transport is a significant concept that underlies a variety of technologies including membrane technology, energy storages, optical, chemical, and biological sensors and ion-mobility exploration techniques. These applications are based on the concepts of capacitance and ion transport, so a prior understanding of capacitance and ion transport phenomena is crucial. In this review, the principles of capacitance and ion transport are described from a theoretical and practical point of view. The review covers the concepts of Helmholtz capacitance, diffuse layer capacitance and space charge capacitance, which is also referred to as quantum capacitance in low-dimensional materials. These concepts are attributed to applications in the electrochemical technologies such as energy storage and excitable ion sieving in membranes. This review also focuses on the characteristic role of channel heights (from micrometer to angstrom scales) in ion transport. Ion transport technologies can also be used in newer applications including biological sensors and multifunctional microsupercapacitors. This review improves our understanding of ion transport phenomena and demonstrates various applications that is applicable of the continued development in the technologies described.

Metode Pengukuran Kapasitansi Dengan Menggunakan Mikrokontroler Arduino Uno

RC circuit (Resistor-Capacitor) is an electric circuit that has a combination of resistor and capacitor components which are installed either series or parallel. This research was conducted to measure the capacitance of two capacitors with different capacitances with only using one resistor. This study aims to compare the capacitance both experimentally (using data acquisition systems) and theoretically. Capacitance measurements were carried out experimentally using Arduino Uno and at a maximum voltage of 5 volts. In this research, it has been successfully determined the charge capacitance of the capacitors, both in experiment and theory. It has been found the correlation of the results between experiment and theory (the value of R2 in charging and discharging process is greater than 0.95).

The role of defects and dimensionality in influencing the charge, capacitance, and energy storage of graphene and 2D materials

The inevitable presence of defects in graphene and other two-dimensional (2D) materials influences the charge density and distribution along with the concomitant measured capacitance and the related energy density. We review, in this paper, the various manifestations of the capacitance including both the classical electrostatic (e.g. associated with double layer, space charge, chemical capacitances) and the quantum forms, as well as a few methodologies to tune the respective capacitances. The role of a proper determination of the surface area of 2D materials, considering the presence of defects, in determining the capacitance and the magnitude of the energy storage is also considered.

Simulation of diffuse-charge capacitance in electric double layer capacitors

We use a Lattice Boltzmann Model (LBM) in order to simulate diffuse-charge dynamics in Electric Double Layer Capacitors (EDLCs). Simulations are carried out for both the charge and the discharge processes on 2D systems of complex random electrode geometries (pure random, random spheres and random fibers). The steric effect of concentrated solutions is considered by using a Modified Poisson–Nernst–Planck (MPNP) equations and compared with regular Poisson–Nernst–Planck (PNP) systems. The effects of electrode microstructures (electrode density, electrode filler morphology, filler size, etc.) on the net charge distribution and charge/discharge time are studied in detail. The influence of applied potential during discharging process is also discussed. Our studies show how electrode morphology can be used to tailor the properties of supercapacitors.