전기적으로 도핑된 나노스케일 장치에서 제1원칙 접근 방식:종합 조사

Evolution of Electrical Doping

Doping means the addition of explicit impurity atoms to the semiconductor. Doping is the intentional addition of atoms to the intrinsic semiconductor to modulate the electrical properties of intrinsic semiconductors. The electrodes sizes are inserted within the script editor, where we assigned the length of the electrode as 1 nm and cross section 0.5 nm × 0.5 nm. Thus, the nominal charge, i.e., ± 0.01, is set for the two electrodes. This script is processed through the job manager, and the calculated doping value for the electrodes is obtained. For this calculation we pursue the following steps:

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Open the New Calculator and select “ATK-SE:Extended Hückel (Device).”

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Uncheck “No SCF iteration.”

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Keep mesh cutoff to 10 Hartree.

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Under “Poisson Solver” set the “Neumann” boundary conditions along A(X) and B(Y) directions.

Figure 5 shows the consolidated form of the comparative study between electrical doping and conventional doping process (using Fe and Ni). This analytical experiment is observed for the thymine nanotube structure which is an example of electrical doping [70]. Fe and Ni atoms are chosen to dope the thymine nanotube, and on the other hand, the molecule is electrically doped [70]. All these results show that amount of electrical doping is much more when compared with conventional doping for little amount of applied bias. Some example works of electrical doping along with its some advantages over conventional doping are discussed in Table 2. It gives a comparative study of electrically doped devices with the existing device modeling which follows the conventional doping method. There are several types of doping, and dopants are available, for example, conventional doping (by adding impurity), electrical doping, co-doping. Generally, two types of dopants are available for conventional doping process, p-type dopants and n-type dopants. They are often called as acceptor and donor impurity atoms. These external impurities are added to the semiconducting materials to enhance their electrical properties mainly conductivity. In the case of the electrical doping process, mainly for analytical modeling using the ATK-VNL approach, we do not proceed with the addition of foreign atoms. Instead of these explicit atom doping, we focus on the change of potential difference at the two ends of the device (mainly at the ends of electrodes). The doping of a semiconductor along with another substance is known as co-doping. For example, when Co and N both are added to MoO₂ nanowires, it will increase the electronic performance of this nanowire [128,129,130]. Various properties like electronic, optical and morphological characteristics of p-doped polyfuran (PF) molecular thin films were investigated by the researchers using a wide range of doping ratios using the electrical doping method. When the doping concentration is ≤ 2%, then it increased the short-circuit current of this PF-based photovoltaic device significantly [44].

Comparative diagram at various electrical dopings along with conventional Fe- and Ni-doping

If we take a close look at the doping concentration from Fig. 6, we can observe that before the year 2000, doping concentration was high, but after that, it becomes lower. Therefore, it can be emphasized that though the device performance has been enhanced, doping concentration is reducing very fast [124, 128, 134,135,136].

Doping concentration year-wise graph

The optical and electrical doping process was also introduced into the silicon with holmium in the year 1999. Intermolecular hybridization state is also governed by the electrical doping process. It was established that for organic semiconductors, molecular electrical doping was found to be at odds when other methods were proved in this field, for example, the formation of polaron. Therefore, the main objective of this study is to propose a polaron-derived state with decreased ionization energy using ultraviolet photoelectrospectroscopy [134]. The electrical doping profile in ferroelectric film capacitors was investigated by the group of researchers using capacitance–voltage measurement. In this experimental study, profiling effect of electrical doping concentration in ferroelectrics was investigated using the following effects of

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A field and spatially dependent permittivity.

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Domain switching analysis of Schottky profiling [135].

From Fig. 7, we can observe the operating temperature for this type of doping-dependent device operation. Though the graph is a little bit complex, it does not obey any specified rule. Therefore, we can conclude it like that temperature requirement is solely depending on the type of materials that are used for this operation.

Temperature for doping

A new model was proposed for the dissociation of carbon atoms at the copper/silica molecular thin layer interface using catalytically hydrogenated graphene meshes using a semipermanent electrical doping method. This process enables stable electronic doping through C–N bonds. Furthermore, the effect of trap states on the electrical doping for organic semiconductors was also investigated. The direct charge transfer process from the trap state of the host molecules to the dopant molecules raised the electrical effect for organic semiconductors. This type of doping process enhances conductivity. Therefore, trap density and energy are also analyzed using impedance spectroscopy [136].

It is observed clearly from Fig. 8 that the thickness of the wafer layers is reducing year wise. The more the time increasing, the layer thickness reduces, and the performance of the device increases.

The thickness of the wafer

Electrically doped and undoped poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) along with tetrafluorotetracyanoquinodimethane films were composed using photoelectron spectroscopy method and also investigated their current–voltage characteristics. Thus, it can be observed that the depletion region was created for the PFO interface. Therefore, the current was increased subsequently [137, 138]. For high-temperature gas sensors, this method of doping plays an important role. The conductivity and gas sensitivity of Ga₂ O₃ thin films was investigated. It was observed that this doping concentration influenced the surface sensitivity [138].

From Fig. 9, it is observed that the cutoff wavelength of the devices reduces sharply within a few decades. Hence, device performance enhanced significantly. Table 3 gives a close look at different characteristics of the devices which follow either electrical doping or conventional doping procedure.

The wavelength of the devices reduces

In this survey, we have reviewed the works which were already established using the electrical doping process. In our works, we used the electrical doping process using the Quantumwise software simulation package in the ATK-VNL atmosphere. The version of this software is 13.8.0. This software simulation is based on first-principle formalisms which is again strongly supported by DFT and NEGF formalisms. Quantumwise is a compact set of atomic-scale modeling tools. These tools were developed in the year of 2003 by some software professionals along with academicians. These ATK-VNL simulations engines help us to calculate the electronic structure as well as to formulate intercorrelations of atomic orbitals. This platform helps us to introduce electrical doping into the molecular level.