Yoke Khin Yap

Michigan Technological University | MTU · Department of Physics

Tellurium can form nanowires of helical atomic chains. With their unique one-dimensional van der Waals structure, these nanowires are expected to show physical and electronic properties that are remarkably different from those of bulk tellurium. Here, we show that few-chain and single-chain van der Waals tellurium nanowires can be isolated using ca...

Plasmon-exciton coupling in hetero-bilayer of WSe2 and WS2 transferred onto Au nanorod arrays is studied. Dark-field scattering measurements reveal that the in-plain dipole moment of excitons in monolayer WS2 allows only the narrow spectral range of 30 nm for the resonant coupling between the localized particle plasmons from Au nanorods and the bri...

Tellurium can form nanowires of helical atomic chains. Given their unique one-dimensional van der Waals structure, these nanowires are expected to show remarkably different physical and electronic properties than bulk tellurium. Here we show that few-chain and single-chain van der Waals tellurium nanowires can be isolated using carbon nanotube and...

This paper investigates the effects of different aging temperatures on the performance of asphalt binders through a comprehensive experimental procedure. Two kinds of asphalt binders with the same 70/100 penetration grade were used in this study. The two types of asphalt binders were short-term aged at three different temperatures: 123°C, 143°C, an...

Metallic gold nanoparticles (Au NPs) with multilayer Au atoms are useful for plasmonic, chemical, medical, and metamaterial application. In this article, we report the opening of the bandgap in substrate-supported two-dimensional (2D) gold quantum dots (Au QDs) with monolayer Au atoms. Calculations based on density functional theory suggest that 2D...

Recycling technology has been widely applied on road pavement due to the aging problem of asphalt binder and the extensive requirement for maintenance. The aim of this research is to use bio-oil generated from sawdust as a rejuvenator to recycle aged asphalt. In this research, the performance graded asphalts PG 58-28 and PG 64-22 were selected as t...

GaSe crystals were grown on graphene domains with few-layer graphene (FLG) grains at the centers of larger monolayer graphene (MLG) grains. We found that GaSe are selectively grown on the MLG and not on the adjacent FLG and the oxidized Si substrates. Nucleation of GaSe was preferentially occurred at the steps of FLG/MLG and MLG/SiO2, due to the pr...

The discovery of monolayer graphene has led to a Nobel Prize in Physics in 2010. This has stimulated research on a wide variety of two-dimensional (2D) layered materials. The coupling of metallic graphene, semiconducting 2D transition metal dichalcogenides (TMDCs) and black phosphorus has attracted tremendous amount of interest in new electronic an...

Since the successful isolation of graphene a little over a decade ago, a wide variety of two-dimensional (2D) layered materials have been studied. They cover a broad spectrum of electronic properties, including metals, semimetals, semiconductors, and insulators. Many of these 2D materials have demonstrated promising potential for electronic and opt...

Field Emission from Zinc Oxide Nanobelt - Volume 23 Issue S1 - A. Asthana, Y. K. Yap, R. S. Yassar

Two-Dimensional Transition-Metal Dichalcogenides Alexander V. Kolobov and Junji Tominaga: Springer, 2016 538 pages, $229.00 (e-book $179.00) ISBN 978-3-319-31449-5

Molybdenum disulfide (MoS₂), as one of the atomically thin two-dimensional transition metal dichalcogenides has novel layer-dependent optical and electronic properties, which make it competitive for potential applications in optoelectronics. Here, we report chemical vapor deposition (CVD) growth of vertically-standing and planar spiral M...

Two-dimensional transition metal dichalcogenides (2D TMDCs) offer several attractive features for use in next-generation electronic and optoelectronic devices. Device applications of TMDCs have gained much research interest, and significant advancement has been recorded. In this review, the overall research advancement in electronic and optoelectro...

The alignment of hexagonal boron-nitride nanotubes (BNNTs) in aqueous KCl solutions under spatially uniform electric fields was examined experimentally, using direct optical visualization to probe the orientation dynamics of individual BNNTs for different electric-field frequencies. Different from most previously studied nanowires and nanotubes, BN...

This presented research investigated the physical properties and accelerated sunlight-healing performance of graphite modified asphalt materials. Two types of graphite materials, flake graphite and exfoliated graphite nanoplatelets (xGNP), were added to asphalt with different contents by weight. Asphalt binder tests were conducted to evaluate the p...

Developing a drug carrier system which could perform targeted and controlled release over a period of time is utmost concern in the pharmaceutical industry. This is more relevant when designing drug carriers for poorly water soluble drug molecules such as curcumin and 6-gingerol. Development of a drug carrier system which could overcome these limit...

Organic pollutants from volatile organic compounds (VOCs), synthetic organic compounds (SOCs), oil spills, and waste disposal have significantly contaminated water and our food chain. The science and engineering of water purification, in particular oil–water separation, has attracted increasing attention in the past five years. As reviewed in this...

This chapter presents an introductory review on properties, synthesis, functionalization, and cutting of boron nitride nanotubes (BNNTs). First, the intriguing properties of BNNTs are highlighted in the perspective of their application in the biomedical field. Then, the developments on the synthesis of BNNTs are summarized. In particular, recent ad...

A comprehensive overview of current research progress on boron nitride nanotubes (BNNTs) is presented in this article. Particularly, recent advancements in controlled synthesis and large-scale production of BNNTs will first be summarized. While recent success in mass production of BNNTs has opened up new opportunities to implement the appealing pro...

For the first time, we report the thermal conductivity of vertically aligned boron nitride nanotube (BNNT) films produced by catalytic chemical vapor deposition. High-quality BNNTs were synthesized at 1200 °C on fused silica substrates precoated with Pt thin-film thermometers. The thermal conductivity of the BNNTs was measured at room temperature b...

The purpose of this study is to use multiple-layer graphite nanoplatelets to modify the asphalt due to the special features of the graphite nanoplatelets. These include the high optical absorption, self-lubrication, and high thermal stability and conductivity. The graphite nanoplatelets with different weight contents (1% and 2%) were slowly added i...

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized bo...

A single-step, room-temperature, and scalable electrophoretic deposition process is reported to form nanocomposites on any electrically conductive surface with metal nanoparticle decorated carbon nanotubes (CNTs). The contact angles (CAs) can be easily tuned from ≈60° to 168° by varying the deposition voltage, while hydrophobicity and superhydropho...

Supercooled water is found to have a significantly enhanced freezing temperature during transient electrowetting with electric fields of order 1 V/μm. High speed imaging reveals that the nucleation occurs randomly at the three-phase contact line (droplet perimeter) and can occur at multiple points during one freezing event. Possible nucleation mech...

Irradiation-induced vacancy defects in multiwalled (MW) boron nitride nanotubes (BNNTs) are investigated via in situ high-resolution transmission electron microscope operated at 80 kV, with a homogeneous distribution of electron beam intensity. During the irradiation triangle-shaped vacancy defects are gradually generated in MW BNNTs under a mediat...

The ever increasing use of nanomaterials in research and commercial products raises concerns for environmental and water contamination. Due to their small size, it is slow and costly to remove nanomaterials from contaminated water by conventional filtration. Here we demonstrate a universal approach to extract one- and two dimensional (1D and 2D) na...

High electron mobility of graphene has enabled their application in high-frequency analogue devices but their gapless nature has hindered their use in digital switches. In contrast, the structural analogous, h-BN sheets and BN nanotubes (BNNTs) are wide band gap insulators. Here we show that the growth of electrically insulating BNNTs on graphene c...

We report here, the in-situ field emission (FE) property measurement on the individual ZnO nanobelts inside a high resolution transmission electron microscope (TEM) using a special scanning tunneling microscopy (STM)-TEM system. The field emission properties were found to be size scale dependent. It was found that the threshold voltage decreases an...

The emergence of two-dimensional (2D) materials has led to tremendous interest in the study of graphene and a series of mono- and few-layered transition metal dichalcogenides (TMDCs). Among these TMDCs, the study of molybdenum disulfide (MoS2) has gained increasing attention due to its promising optical, electronic, and optoelectronic properties. O...

The inherent problem of a zero-band gap in graphene has provided motivation to search for the next-generation electronic materials including transition metal dichalcogenides, such as MoS2. In this study, a triangular MoS2 quantum dot (QD) is investigated to see the effects of passivation, additional layer, and the h-BN substrate on its geometry, en...

Boron nitride (BN) nanostructures can have varied structures. They can simply be nanoscale particles of various bulk BN materials, including hexagonal-phase BN (h-BN) and cubic-phase BN (c-BN). However, many of the BN nanostructures of popular interest were discovered in the past 20 years and are unique in their structures and properties. These inc...

Boron nitride (BN) nanostructures can have varied structures. ey can simply be nanoscale particles of various bulk BN materials, including hexagonal-phase BN (h-BN) and cubic-phase BN (c-BN). However, many of the BN nanostructures of popular interest were discovered in the past 20 years and are unique in their structures and properties. ese include...

The detection of piezoelectric current in one-dimensional semiconductor materials has been a controversial issue due to the possibility of charge annihilation at nanoscale dimensions. We report here, the mechanically triggered electrical current in uniaxially compressed individual ZnO nanobelts under no applied bias. The measurements were carried o...

In this study, we investigate the charge-transport behavior in a disordered one-dimensional (1D) chain of metallic islands using the newly developed multi-island transport simulator (MITS) based on semi-classical tunneling theory and kinetic Monte Carlo simulation. The 1D chain is parameterized to model the experimentally-realized devices studied b...

In this study, we investigate the charge-transport behavior in a disordered one-dimensional (1D) chain of metallic islands using the newly developed multi-island transport simulator (MITS) based on semi-classical tunneling theory and kinetic Monte Carlo simulation. The 1D chain is parameterized to model the experimentally-realized devices studied b...

Clusters of diamond-phase carbon, known as nanodiamonds, exhibit novel mechanical, optical and biological properties that have elicited interest for a wide range of technological applications. Although diamond is predicted to be more stable than graphite at the nanoscale, extreme environments are typically used to produce nanodiamonds. Here we show...

One-dimensional arrays of gold quantum dots (QDs) on insulating boron nitride nanotubes (BNNTs) can form conduction channels of tunneling field-effect transistors. We demonstrate that tunneling currents can be modulated at room temperature by tuning the lengths of QD-BNNTs and the gate potentials. Our discovery will inspire the creative use of nano...

Hetero-junctions of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) are expected to have appealing new properties that are not available from pure BNNTs and CNTs. Theoretical studies indicate that BNNT/CNT junctions could be multifunctional and applicable as memory, spintronic, electronic, and photonics devices with tunable band structu...

The mechanical properties of individual multiwall boron nitride nanotubes (MWBNNTs) synthesized by a growth-vapor-trapping chemical vapor deposition method are investigated by a three-point bending technique via atomic force microscopy. Multiple locations on suspended tubes are probed in order to determine the boundary conditions of the supported t...

Novel PMMA-STO-CNT matrices were created by opened tip vertically-aligned multiwalled carbon nanotubes (VA-MWCNTs) with conformal coating of strontium titanate (STO) and Poly(methyl methacrylate) (PMMA). Emission threshold of 0.8 V/μm was demonstrated, about five-fold lower than that of the as-grown VA-MWCNTs. This was obtained after considering th...

This paper aims to investigate the viability of using swine waste binder to improve the rheological properties of bituminous asphalt binder. Due to rising bituminous asphalt binder costs, diminishing reserves of crude oil from which asphalt binder is derived, and the gradual paradigm shift toward more environmentally friendly and energy efficient h...

In this work, piezoelectricity of individual ZnO nanobelts grown along the [0 1 ī 0] direction is studied using piezoresponse force microscopy (PFM). It is found that the effective piezoelectric coefficient of these NBs, $d_{33}^{\mathrm{eff}}$ , is increasing from 2.7 pm/V at 30 kHz to 44 pm/V at 150 kHz. The results were explained by the Debye...

The objective of this study is to evaluate the rheological properties and chemical bonding of nano-modified asphalt binders blended with nanosilica. In this study, the nanosilica was added to the control asphalt at contents of 4% and 6% based on the weight of asphalt binders. Superpave binder and mixture tests were utilized in this study to estimat...

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Ambipolar behaviors of zinc oxide nanowires (ZnO NWs) are obtained for the first time by controlled annealing in hydrogen ambient. Optimum annealing can create p-type acceptors into ZnO NWs while maintaining the n-type donors from the as-grown samples. We found that such optimum condition must be one that is more than sufficient to eliminate the gr...

The electrical properties of boron nitride (BN) nanostructures, particularly BN nanotubes (NTs), have been studied less in comparison to the counterpart carbon nanotubes. The present work investigates the field emission (FE) behavior of BNNTs under multiple cycles of FE experiments and demonstrates a strain-engineering pathway to tune the electroni...

Nanowires of indium tin oxide (ITO) were grown on catalyst-free amorphous glass substrates at relatively low temperature of 250 °C in argon and helium ambient by the Nd:YAG pulsed laser deposition technique. All the ITO samples showed crystalline structure due to substrate heating and the (400) X-ray diffraction peak became relatively stronger as t...

High-quality boron nitride nanotubes (BNNTs) were functionalized for the first time with water-soluble and biocompatible PEGylated phospholipid [methoxy-poly(ethylene glycol)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N conjugates (mPEG-DSPE)]. We found that BNNTs can be suspended in water for more than 3 months without precipitation. By compa...

Low-temperature growth of indium tin oxide (ITO) nanowires (NWs) was obtained on catalyst-free amorphous glass substrates at 250 °C by Nd:YAG pulsed-laser deposition. These ITO NWs have branching morphology as grown in Ar ambient. As suggested by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), our IT...

Superhydrophobic surfaces are attractive as self-cleaning protective coatings in harsh environments with extreme temperatures and pH levels. Hexagonal phase boron nitride (h-BN) films are promising protective coatings due to their extraordinary chemical and thermal stability. However, their high surface energy makes them hydrophilic and thus not ap...

We report here investigations of crystal and electronic structure of as-synthesized and annealed ZnO nanobelts by an in-situ high-resolution transmission electron microscope equipped with a scanning tunneling microscopy probe. The in-situ band gap measurements of individual ZnO nanobelts were carried out in scanning tunneling spectroscopy mode usin...

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

In this investigation, the size-scale in mechanical properties of individual [0001] ZnO nanowires and the correlation with atomic-scale arrangements were explored via in situ high-resolution transmission electron microscopy (TEM) equipped with atomic force microscopy (AFM) and nanoindentation (NI) systems. The Young's modulus was determined to be s...

First-principles calculations based on density functional theory are performed on graphene/BN and BN bilayers to investigate the effect of the strain on their energy gaps. For the graphene/BN bilayer, the bands have characteristic graphenelike features with a small band gap at K. Application of strain modulates the band gap, whose magnitude depends...

Field emission from as-grown carbon nanotube (CNTs) films often suffered from high threshold electric field, and low emission site density due to screening effects. These problems can be resolved by patterned growth of CNTs on lithographically prepared catalyst films. However, these approaches are expensive and not applicable for future emitting de...

ZnO nanostructures have proven to be versatile functional materials with promising electronic, piezoelectric and optical properties. Here, we report on the application of (CdSe) ZnS Core Shell quantum dots decorated ZnO Nanowires (ZnONWs) and Nanobelts (NBs) in solar energy harvesting. Results indicate that both as grown and decorated ZnO Nanostruc...

The recent observation of high flexibility in buckled boron nitride nanotubes (BNNTs) contradicts the pre-existing belief about BN nanotube brittleness due to the partially ionic character of bonding between the B and N atoms. However, the underlying mechanisms and relationships within the nanotube remained unexplored. This study reports for the fi...

Vertically-aligned multi-walled carbon nanotubes (CNTs) were grown on stainless steel (SS) mesh by thermal chemical vapor deposition with a diffusion barrier of Al2O3 film. These three-dimensional porous structures (SS-CNT meshes) were found to be superhydrophobic and superoleophilic. Water advancing contact angles of 145–150° were determined for t...

Plasma enhanced chemical vapor deposition (PECVD) is a unique technique for growing vertically-aligned multiwall carbon nanotubes (VA-MWNTs) at controllable tube densities. This technique is of considerable importance for low temperature growth of VA-MWNTs at desired locations. However, the graphitic order of these MWNTs is inferior to those grown...

The growth of ZnO nanotubes and nanosquids is obtained by conventional thermal chemical vapor deposition (CVD) without the use of catalysts or templates. Characterization of these ZnO nanostructures was conducted by X-ray powder diffraction (XRD), Field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and photoluminescence (PL). R...

For the first time, patterned growth of boron nitride nanotubes (BNNTs) on Si substrates has been achieved by catalytic chemical vapor deposition (CCVD). Following the boron oxide chemical pathway and our growth vapor trapping approach, high quality and quantity BNNTs can be produced. Effective catalysts have been found to facilitate the growth of...

The effects of AC field strength and AC frequency on the density of dielectrophoretically deposited multi-walled carbon nanotubes (MWCNTs) were investigated and explained in terms of existing theory. We show that while both parameters can be used to control deposition density, the experimentally observed frequency trend can not be explained by the...

This article provides a concise review of the recent research advancements in boron nitride nanotubes (BNNTs) with a comprehensive list of references. As the motivation of the field, we first summarize some of the attractive properties and potential applications of BNNTs. Then, latest discoveries on the properties, applications, and synthesis of BN...

We have created PMMA-CNT matrices by embedding opened-tip vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) with poly(methyl methacrylate) (PMMA). These PMMA-CNT matrices are excellent electron field emitters with an emission threshold field of 1.675 V/μm, more than 2-fold lower that that of the as-grown sample. In addition, the emission...

Selective growth of boron nitride nanotubes (BNNTs) was demonstrated by plasma-enhanced pulsed laser deposition (PE-PLD). Although PLD is a physical vapor deposition technique for the growth of boron nitride (BN) thin films, ion sputtering induced by the plasma can eliminate the formation of BN thin films and lead to the so-called total resputterin...