Kar Seng Teng

Swansea University | SWAN · Department of Electrical & Electronic Engineering

Ultraviolet (UV) photodetectors have gained much attention due to their numerous important applications ranging from environmental monitoring to space communication. To date, most p‐NiO/n‐Si heterojunction photodetectors (HPDs) exhibit poor UV responsivity and slow response. This is mainly due to a small valence band offset (ΔEV) at the NiO/Si inte...

Lead sulfide colloidal quantum dots (PbS CQDs) are promising optoelectronic materials due to their unique properties, such as tunable band gap and strong absorption, which are of immense interest for application in photodetectors and solar cells. However, the tunable band gap of PbS CQDs would only cover visible short-wave infrared; the ability to...

The tunable band gap of PbS colloidal quantum dots (CQDs) from ultraviolet (UV) to short-wave infrared (SWIR) bands provides many potential applications in optoelectronics. However, synthesis of large-sized CQDs that exhibit good stability and sensitivity for extended wavelength still remains a technological challenge. In this paper, a novel broadb...

The ultraviolet (UV) photodetector has found many applications, ranging from optical communication to environmental monitoring. There has been much research interest in the development of metal oxide-based UV photodetectors. In this work, a nano-interlayer was introduced in a metal oxide-based heterojunction UV photodetector to enhance the rectific...

Quantum dots have found significant applications in photoelectric detectors due to their unique electronic and optical properties, such as tunable bandgap. Recently, colloidal quantum dots (CQDs) have attracted much interest because of the ease of controlling the dot size and low production cost. In this paper, a high-performance ZnO/PbS heterojunc...

Ultraviolet (UV) photodetector has found extensive applications, ranging from optical communication to ozone sensing. Wide bandgap metal oxide heterostructures have gained significant interest in the development of UV photodetectors due to their excellent electronic and optical properties, as well as ease of fabrication. However, there are surface...

Combining novel two-dimensional (2D) materials with traditional semiconductors to form heterostructures for photoelectric detection have attracted great attention due to their excellent photoelectric properties. In this study, we reported the formation of a heterostructure comprising of tin telluride (SnTe) and germanium (Ge) by a simple and effici...

Photodetectors are receiving increasing attention because of their widely important applications. Therefore, developing broadband high-performance photodetectors using new materials that can function at room temperature has become increasingly important. As a functional material, tin telluride (SnTe), has been widely studied as a thermoelectric mat...

Silicon quantum dots (Si-QDs) are excellent luminescent material due to its unique optoelectronic properties and have huge application potential in the field of photodetection. Recently, there has been much research interests in developing low-cost, facile and environmentally friendly methods to prepare the nanomaterials in addition to yielding exc...

Ability to mass produce graphene at low cost is of paramount importance in bringing graphene based technologies into market. Here we report a facile liquid-phase catalytic growth of graphene suitable for mass production. Iodine tincture is used to catalyze graphene quantum dots to form graphene films at room temperature. Such method has many advant...

Two-dimensional (2D) materials exhibit many unique optical and electronic properties that are highly desirable for application in optoelectronics. Here, we report the study of photodetector based on 2D Bi2O2Te grown on n-Si substrate. The 2D Bi2O2Te material was transformed from sputtered Bi2Te3 ultrathin film after rapid annealing at 400 ℃ for 10...

Two-dimensional (2D) materials exhibit many unique optical and electronic properties that are highly desirable for application in optoelectronics. Here, we report the study of photodetector based on 2D Bi2O2Te grown...

The ability to mass produce graphenes at low cost is of paramount importance in bringing graphene-based technologies into market. Herein, we report the facile liquid-phase catalytic growth of graphene suitable for mass production. Iodine tincture was used to catalyze graphene quantum dots into graphene films at room temperature. This method has man...

Tantalum disulfide (TaS 2 ) two-dimensional film material has attracted wide attention due to its unique optical and electrical properties. In this work, we report the preparation of 1 T-TaS 2 quantum dots (1 T-TaS 2 QDs) by top-down method. Herein, we prepared the TaS 2 QDs having a monodisperse grain size of around 3 nm by an effective ultrasonic...

Abstract Ultraviolet (UV) photodetector has attracted extensive interests due to its wide-ranging applications from defense technology to optical communications. The use of wide bandgap metal oxide semiconductor materials is of great interest in the development of UV photodetector due to their unique electronic and optical properties. In this work,...

GeTe is an important narrow bandgap semiconductor material and has found application in the fields of phase change storage as well as spintronics devices. However, it has not been studied for application in the field of infrared photovoltaic detectors working at room temperature. Herein, GeTe nanofilms were grown by magnetron sputtering technique a...

Graphene exhibits excellent physical, electronic and chemical properties that are highly desirable for biosensing application. However, most graphene biosensors are based on graphene lying flat on a substrate and therefore not utilizing its maximum specific surface area for ultra-sensitive detection. Herein, we showcased the novel use of photonic a...

With the rapid development of optoelectronic devices, photodetectors have triggered an unprecedented promising in the field of optical communication, environmental monitoring, biological imaging, chemical sensing. At the same time, there is a higher requirement for photodetectors. It is still a huge challenge for photodetectors that possess excelle...

Hydrothermal growth of ZnO nanowires has been of great interest as it allows the use of organic substrates for flexible electronics applications. However, there are drawbacks on the growth technique as it is known to introduce defects in the nanowires. In this work, the use of intense pulsed light on hydrothermally grown ZnO nanowires on polyimide...

Zinc sulfide (ZnS) quantum dots (QDs) were synthesized using a facile, low-cost and environmentally friendly method at room temperature and ambient pressure. The structural, optical and electrical properties of the as-prepared ZnS QDs were investigated. The monodispersed crystalline ZnS QDs with an average size of 3.8 nm has been prepared, an absor...

GeTe is an important narrow bandgap semiconductor material and has found application in the fields of phase change storage as well as spintronics devices. However, it has not been studied for application in the field of infrared photovoltaic detectors working at room temperature. Herein, GeTe nanofilms were grown by magnetron sputtering technique a...

GeTe is an important narrow bandgap semiconductor material and has found application in the fields of phase change storage as well as spintronics devices. However, it has not been studied for application in the field of infrared photovoltaic detectors working at room temperature. Herein, GeTe nanofilms were grown by magnetron sputtering technique a...

GeTe is an important narrow band gap semiconductor material, which has found application in the fields of thermoelectricity, phase change storage as well as switch. However, it has not been studied for application in the field of photodetectors. Here, GeTe thin films were grown by magnetron sputtering and their material structure, optical and elect...

SnOx thin films with tunable optical bandgap were prepared using RF magnetron sputtering. The bandgap was adjustable between 2.16 and 3.96 eV depending on oxygen partial pressure during deposition and heat treatment. The structure and properties of the SnOx films were studied. The optical absorption of the SnOx films covered multiple ultraviolet ba...

Abstract Low-dimensional semiconductors exhibit remarkable performances in many device applications because of their unique physical, electrical, and optical properties. In this paper, we report a novel and facile method to synthesize In2S3 quantum dots (QDs) at atmospheric pressure and room temperature conditions. This involves the reaction of sod...

Irreversible organ damage or even death frequently occurs when humans or animals unknowingly drink contaminated water. Therefore, in many countries drinking water is disinfected to ensure removal of harmful pathogens from drinking water. If upstream water treatment prior to disinfection is not adequate, disinfection byproducts (DBPs) can be formed....

Graphene has been widely used as electrodes and active layers in optoelectronics due to its diverse excellent performances, such as high mobility, large thermal conductivity, and high specific surface area. Methodology for constructing p–n junction has become an important consideration in improving the performance of optoelectronic devices and broa...

Cadmium sulfide quantum dots (CdS QDs) are widely used in solar cells, light emitting diodes, photocatalysis, and biological imaging because of their unique optical and electrical properties. However, there are some drawbacks in existing preparation techniques for CdS QDs, such as protection of inert gas, lengthy reaction time, high reaction temper...

Tin sulfide quantum dots (SnS 2 QDs) are n-type wide band gap semiconductor. They exhibit a high optical absorption coefficient and strong photoconductive property in the ultraviolet and visible regions. Therefore, they have been found to have many potential applications, such as gas sensors, resistors, photodetectors, photocatalysts, and solar cel...

Graphene quantum dots (GQDs) have been widely studied in recent years due to its unique structure-related properties, such as optical, electrical and optoelectrical properties. GQDs are considered new kind of quantum dots (QDs), as they are chemically and physically stable because of its intrinsic inert carbon property. Furthermore, GQDs are enviro...

Due to increasing stringency of water legislation and extreme consequences that failure to detect some contaminants in water can involve, there has been a strong interest in developing electrochemical biosensors for algal toxins detection during last decade, evidenced by literature increasing from 2 journal papers pre-2009 to 24 between 2009 and 20...

Herein, we report an effective and simple method for producing Tellurium Quantum dots (TeQDs), zero-dimensional nanomaterials with great prospects for biomedical applications. Their preparation is based on the ultrasonic exfoliation of Te powder dispersed in 1-methyl-2-pyrrolidone. Sonication causes the van der Waals forces between the structural h...

A three electrode electrochemical enzymatic biosensor consisting of ZnO nanowires was successfully fabricated using flexographic printing technique. The incorporation of ZnO nanowires at the working electrode provides advantages such as simple functionalization and high surface area for enhanced sensitivity. The flexographic printing technique allo...

In this work, the formation of a nanotextured surface is reported on flexographic printed zinc oxide thin films which provide an excellent platform for low-cost, highly sensitive biosensing applications. The ability to produce nanotextured surfaces using a high throughput, roll-to-roll production method directly from precursor ink without any compl...

A polymeric carbon nitride (g-C3N4) nanosheets/graphene hybrid phototransistor designed for the near-UV regime is reported. Efficient transfer of electrons from g-C3N4 to graphene is observed under illumination. The devices show a responsivity in the order of 103 A W−1 with a large and reproducible photocurrent. The hybrid is found stable after sto...

In this paper, we have presented the use of flexographic printing techniques in the selective patterning of gold nanoparticles (AuNPs) onto a substrate. Highly uniform coverage of AuNPs was selectively patterned on the substrate surface, which was subsequently used in the development of a glucose sensor. These AuNPs provide a biocompatible site for...

The thermal annealing of zinc precursors to form suitable seed layers for the growth of ZnO nanowires is common. However, the process is relatively long and involves high temperatures which limit substrate choice. In this study the use of a low temperature, ultra-violet (UV) exposure is demonstrated for photodecomposition of zinc acetate precursors...

Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. PANI-GQD based photodetector exhibit higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetector. The improved photoresponse is attributed...

Graphene quantum dot–polyaniline (PANI–GQD) composite films were synthesized by a chemical oxidation polymerization process. The optical properties of the PANI–GQD composite were studied by varying the mole concentration of PANI and the size of the GQDs. The Au/PANI–GQDs/ITO sandwich device was fabricated in order to investigate the transport prope...

Material that can emit a broad spectral wavelengths covering deep ultraviolet (DUV), visible, and near infrared (NIR) is highly desirable. It can lead to important applications such as broadband modulators, photodetectors, solar cells, bioimaging, and fiber communications. However, there is currently no material that meets such desirable requiremen...

Advances in the controlled assembly of nanoscale building blocks have resulted in functional devices which can find applications in electronics, biomedical imaging, drug delivery etc. In this study, novel covalent nanohybrid materials based upon [Ru(bpy)3](2+)-doped silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs), which could be conditi...

Doping of carbon-based materials is of great importance due to its ability to modulate the optical, electrical, and optoelectronic properties. Nitrogen-doped graphene quantum dots (N-GQDs) has received significant attention due to its superior electrocatalytic activity, optical properties and biocompatibility. The energy-level structure of N-GQDs r...

It is of scientific importance to obtain graphene quantum dots (GQDs) with narrow-size distribution in order to unveil their size-dependent structural and optical properties, thereby further to explore the energy band diagram of GQDs. Here, a soft-template microwave-assisted hydrothermal method to prepare GQDs with diameters less than 5 nm ± 0.55 n...

In this study, the use of flexographic printing was investigated for low cost, high volume production of devices incorporating nanowires through the printing of zinc acetate precursors on a substrate used to form zinc oxide (ZnO) seeds for the growth of nanowires using a hydrothermal growth technique. The printing of precursors allows the selective...

Graphene quantum dots (GQDs) have attracted great attention due to their unique optoelectronic properties. There remains a critical challenge to utilize the water-soluble GQDs for device applications. Here we report a facile method to fabricate a GQD–agar composite. The composite exhibits excellent optical stability and no luminescence quenching is...

Quasi-aligned hexagonal Mg-doped aluminum nitride zigzag nanowires (AlN:Mg ZNWs) were fabricated on sapphire substrates using chemical vapor deposition method. A saturated magnetic moment of ∼1 emu/cm3 was found in the AlN:Mg ZNWs when a magnetic field was applied parallel to the sample. The AlN:Mg ZNWs exhibited magnetic anisotropy. The magnetic m...

Glucose-derived water-soluble crystalline graphene quantum dots (GQDs) with an average diameter as small as 1.65 nm (∼5 layers) were prepared by a facile microwave-assisted hydrothermal method. The GQDs exhibits deep ultraviolet (DUV) emission of 4.1 eV, which is the shortest emission wavelength among all the solution-based QDs. The GQDs exhibit ty...

Graphene oxide nanosheets (GONs) have attracted considerable interest due to their potential applications in electronic and optoelectronic devices. Graphene oxide (GO) is usually prepared by using Hummers' method or modified Hummers' methods, which require graphite and strong oxidizers, followed by exfoliation to obtain GONs. The main drawbacks of...

A single-mode buried heterostructure laser has been imaged using Cross-Sectional Scanning Tunneling Microscopy (X-STM). The problem of positioning the tip on the restricted active region on the (110) face has been overcome using combined Scanning Electron Microscopy (SEM). In order to understand the change in the STM scans when biased, particularly...

A microdielectric resonator antenna of dimensions (100 × 100 × 500 m) is designed for biosensing applications. The antenna is terminated with a thin layer of gold on the top and bottom of the microstructure for achieving a high Q . On top of the antenna is the sensing region (100 μm³), which loads the antenna depending on the type of mat...

Mn doped ZnO (ZnO:Mn) thin films with ~ 10 at.% of Mn were grown on quartz substrates by filtered cathodic vacuum arc (FCVA) technique at low substrate temperature (≤ 200 °C). The influence of substrate temperature and oxygen flow rate on the optical, electrical and magnetic properties of the ZnO:Mn thin films was studied. Both room temperature fer...

Cross-sectional scanning tunneling microscopy is used to study defects on the surface of semiconductor laser devices. Step defects across the active region caused by the cleave process are identified. Curved blocking layers used in buried heterostructure lasers are shown to induce strain in the layers above them. Devices are also studied whilst pow...

Cross-sectional scanning tunneling microscopy (STM) has been used to study in-operation changes that occur at the active region of clean-cleaved semiconductor laser diodes. A tunneling model that allows the inclusion of tip-induced band bending and surface defect states has been used to study the origin of the surface changes which give rise to the...

DOI: 10.1063/1.3176434 Carbon-doped ZnO (ZnO:C) thin films exhibiting Curie temperature above room temperature were fabricated using ion beam technique. The magnetic moment of the ZnO:C films was found to be around 1.35 μB per carbon atom. The ZnO:C films showed p-type conduction with a hole concentration of ~5 X 10¹⁷ cm⁻³. In addition, the anomalo...

Ferromagnetic and highly conductive copper doped ZnO (ZnO:Cu) films were prepared by filtered cathodic vacuum arc technique. By employing a biasing technique during growth, the electron concentration and resistivity of the ZnO:Cu films can be as high as 10²⁰ cm ^-3 and 5.2×10^-3 Ω  cm , respectively. The ferromagnetic...

Using a near-field scanning optical microscope, near-field photocurrent and topographic imaging has measured the effect on intrinsic electric fields and photocurrent propagation resulting from inserting multi-quantum barrier (MQB) super-lattices into quantum well lasers. Measurements on devices at two different excitation wavelengths have highlight...

The silicon carbide (SiC) surface is more complex than that of silicon and can be carbon-terminated or silicon-terminated, and can exist as several reconstructions. Investigations of the surface structure as a function of temperature, under ultrahigh vacuum (UHV) conditions using scanning tunneling microscopy (STM) and low energy electron diffracti...

The formation of the Ni/Al0.2Ga0.8N Schottky contacts has been investigated by x-ray photoelectron spectroscopy. In situ scanning tunneling microscopy was used in parallel to investigate the morphology of the Ni covered surface after the last deposition. In the same way, results are presented through two perspectives: the intensity of core-level si...

Au/Cr Ohmic contacts on p-type, heavily boron-doped, single-crystal CVD diamond have been studied using X-ray photoelectron spectroscopy (XPS) and electrical measurements. The interaction of chromium, a carbide-forming metal, with the diamond surface is discussed. The Cr/diamond contact formation process has been studied as a function of chromium t...

Semiconductor devices which utilize the quantum confinement of charge carriers inherently employ material layers thin enough that even monolayer interface roughness has an effect on performance. We present a method for including the effect of interface roughness on the calculation of electron energy levels and wavefunctions by solving Schrödinger’s...