Promising Materials For Future Electronics Research Articles

Synthesis of conducting water-dispersible polyaniline particles and its template-guided patterning

Organic conductors are a promising material for future electronics. Although, its processing is a big challenge. In this manuscript, we demonstrate micropatterning of polyaniline within the pores of a polycarbonate membrane to fabricate a device for a conductometric sensor. The aqueous dispersion of polyaniline particles was prepared by single pot oxidative polymerization of aniline monomer using dodecylbenzene sulfonic acid as a surfactant as well as a dopant, and the polyaniline from its aqueous dispersion was then precipitated within the pores of polycarbonate membrane by adding solvents of varying polarities. The phase diagram of precipitation was drawn by titrating the polyaniline dispersion with tetrahydrofuran solvent. The dispersion was characterized by Fourier transform infrared spectroscopy and UV-Vis spectroscopy, as well as a transmission electron microscope. The molecular weight of the synthesized polyaniline was measured by gel permission chromatography. The morphology of polyaniline has been compared through transmission electron microscopy in its dispersed form and after precipitation. Field emission scanning electron microscopy was used to see the growth of channel formation of precipitated polyaniline within the pores of the polycarbonate membrane. The electroactivity of the precipitated polyaniline was measured by in-situ conductance measurement as a function of the electrochemical state.

Role of flexural phonons in carrier mobility of two-dimensional semiconductors: free standing vs on substrate

Two-dimensional (2D) semiconductor is a promising material for future electronics. It is believed that the flexural phonon (FP) induced scattering plays an important role in the room-temperature carrier mobility, and the substrate can significantly affect such scattering. Here we develop an ‘implicit’ substrate model, which allows us to effectively quantify different effects of the substrate on the FP scattering. In conjunction with the first-principles calculations, we study the intrinsic mobilities of the holes in Sb and electrons in MoS2 as representative examples for 2D semiconductors. We find that the FP scattering is not dominant and is weaker than other scatterings such as that induced by longitudinal acoustic (LA) phonon. This is due to the significantly smaller electron–phonon-coupling (EPC) matrix elements for the FP compared with that for the LA phonon in the free-standing case; although the substrate enhances the FP EPC, it suppresses the FP population, making the FP scattering still weaker than the LA scattering. Our work improves the fundamental understanding of the role of FP and its interaction with the substrate in carrier mobility, and provides a computational model to study the substrate effects.

Growth and Interlayer Engineering of 2D Layered Semiconductors for Future Electronics.

Layered materials that do not form a covalent bond in a vertical direction can be prepared in a few atoms to one atom thickness without dangling bonds. This distinctive characteristic of limiting thickness around the sub-nanometer level allowed scientists to explore various physical phenomena in the quantum realm. In addition to the contribution to fundamental science, various applications were proposed. Representatively, they were suggested as a promising material for future electronics. This is because (i) the dangling-bond-free nature inhibits surface scattering, thus carrier mobility can be maintained at sub-nanometer range; (ii) the ultrathin nature allows the short-channel effect to be overcome. In order to establish fundamental discoveries and utilize them in practical applications, appropriate preparation methods are required. On the other hand, adjusting properties to fit the desired application properly is another critical issue. Hence, in this review, we first describe the preparation method of layered materials. Proper growth techniques for target applications and the growth of emerging materials at the beginning stage will be extensively discussed. In addition, we suggest interlayer engineering via intercalation as a method for the development of artificial crystal. Since infinite combinations of the host-intercalant combination are possible, it is expected to expand the material system from the current compound system. Finally, inevitable factors that layered materials must face to be used as electronic applications will be introduced with possible solutions. Emerging electronic devices realized by layered materials are also discussed.

Atomic layer deposition of a uniform thin film on two-dimensional transition metal dichalcogenides

Two-dimensional transition metal dichalcogenides (2D TMDs) is one of the promising materials for future electronics since they have, not only superior characteristics, but also a versatility that conventional materials do not have with a few nanometer thickness. One of the prerequisites for applying these materials to device fabrication is to deposit an ultrathin film below 10 nm with excellent uniformity. However, TMD has quite a different surface chemistry and is fragile to external conditions compared to conventional materials. Thus, thin film deposition on 2D TMD with excellent uniformity using conventional deposition techniques is quite challenging. Currently, the most adequate deposition technique for sub-10 nm-thick film growth is atomic layer deposition (ALD). A thin film is formed on the surface by the reaction between chemical and surface species based on the self-limiting growth manner. Owing to its unique and superior growth characteristics, such as excellent uniformity and conformality, ALD is an essential deposition technique for nanoscale device fabrication. However, since 2D TMD has a lack of reaction sites on the surface, various studies have reported that ALD on 2D TMDs surfaces without any treatment showed an island growth mode or formation of clusters rather than continuous films. For this reason, recent studies have been focused on the deposition of an ultrathin film on 2D TMDs with excellent uniformity. For a decade, there have been various approaches to obtain uniform films on 2D TMDs using ALD. Among them, the authors focus on the most frequently researched methods and adsorption control of chemical species by modifying the process parameters or functionalization of new chemical species that can assist adsorption on the chemically inert 2D TMD surface. In this review, the overall research progress of ALD on 2D TMD will be discussed which would, in turn, open up new horizons in future nanoelectronics fabrication using 2D TMDs.

Substrate dielectric effects on graphene field effect transistors

Graphene is emerging as a promising material for future electronics and optoelectronics applications due to its unique electronic structure. Understanding the graphene-dielectric interaction is of vital importance for the development of graphene field effect transistors (FETs) and other novel graphene devices. Here, we extend the exploration of substrate dielectrics from conventionally used thermally grown SiO2 and hexagonal boron nitride films to technologically relevant deposited dielectrics used in semiconductor industry. A systematic analysis of morphology and optical and electrical properties was performed to study the effects of different substrates (SiO2, HfO2, Al2O3, tetraethyl orthosilicate (TEOS)-oxide, and Si3N4) on the carrier transport of chemical vapor deposition-derived graphene FET devices. As baseline, we use graphene FETs fabricated on thermal SiO2 with a relatively high carrier mobility of 10 000 cm2/(V s). Among the deposited dielectrics studied, silicon nitride showed the highest mobility, comparable to the properties of graphene fabricated on thermal SiO2. We conclude that this result comes from lower long range scattering and short range scattering rates in the nitride compared those in the other deposited films. The carrier fluctuation caused by substrates, however, seems to be the main contributing factor for mobility degradation, as a universal mobility-disorder density product is observed for all the dielectrics examined. The extrinsic doping trend is further confirmed by Raman spectra. We also provide, for the first time, correlation between the intensity ratio of G peak and 2D peak in the Raman spectra to the carrier mobility of graphene for different substrates.

Nonzero Gap Two-Dimensional Carbon Allotrope from Porous Graphene

Graphene is considered one of the most promising materials for future electronics. However, in its pristine form, graphene is a gapless material, which imposes limitations to its use in some electronic applications. To solve this problem, many approaches have been tried, such as physical and chemical functionalizations. These processes compromise some of the desirable graphene properties. In this work, based on ab initio quantum molecular dynamics, we showed that a two-dimensional carbon allotrope, named biphenylene carbon (BPC), can be obtained from selective dehydrogenation of porous graphene. BPC presents a nonzero bandgap and well-delocalized frontier orbitals. Synthetic routes to BPC are also addressed.

A Nonzero Gap Two-dimensional Carbon Allotrope from Porous Graphene

ABSTRACTGraphene has been one of the hottest topics in materials science in the last years. Because of its special electronic properties graphene is considered one of the most promising materials for future electronics. However, in its pristine form graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Many approaches have been tried to create, in a controlled way, a gap in graphene. These approaches have obtained limited successes. Recently, hydrogenated graphene-like structures, the so-called porous graphene, have been synthesized. In this work we show, based on ab initio quantum molecular dynamics calculations, that porous graphene dehydrogenation can lead to a spontaneous formation of a nonzero gap two-dimensional carbon allotrope, called biphenylene carbon (BC). Besides exhibiting an intrinsic nonzero gap value, BC also presents well delocalized frontier orbitals, suggestive of a structure with high electronic mobility. Possible synthetic routes to obtain BC from porous graphene are addressed.