Graphene growth at low temperatures using RF-plasma enhanced chemical vapour deposition

The advantage of plasma enhanced chemical vapour deposition (PECVD) method is the ability to deposit thin films at relatively low temperature. Plasma power supports the growth process by decomposing hydrocarbon to carbon radicals which will be deposited later on metal catalyst. In this work, we have successfully synthesis graphene on Ni and Co films at relatively low temperature and optimize the synthesis conditions by adjusting the plasma power. Low temperature growth of graphene was optimized at 600°C after comparing the quality of as-grown graphene at several temperatures from 400 to 800°C and by varying plasma powers in the range of 20 - 100 W. Raman analysis of the as-grown samples showed that graphene prefers lower plasma power of 40 W. The annihilation of graphene formation at higher plasma powers is attributed to the presence of high concentration of hydrogen radical from methane which recombines with carbon elements on thin film surface. The optimum graphene growth conditions were obtained at growth temperature of 600°C, plasma power of 40 W and growth time of 10 min with methane flow rate of 120 sccm

Potential of irradiated high density polyethylene/ethylene propylene rubber-carbon nanotube nanocomposite as shoe sole

The material selection for shoe soles is important as it determines the long-term performance of sports shoes, especially the performances of athletes’ shoes with respect to comfort during walking, running and jumping. An effective approach is developed to establish a strong interface between the carbon nanotube and high-density polyethylene/ethylene propylene rubber matrix by introducing electron beam radiation to the nanocomposite as a crosslinking technique. This study focuses on the carbon nanotube variation in the polymer matrix of high-density polyethylene and ethylene propylene rubber. The mechanical properties of high-density polyethylene/ethylene propylene rubber–carbon nanotube nanocomposites with different carbon nanotube contents were investigated at 0.5, 1, 3 and 5 wt% of carbon nanotube content. The combinations of nanofillers and polymer matrix stimulate the performance of sports shoes soles since each of them exhibits superior properties. The aim of this article is to find the optimum carbon nanotube content over the mechanical properties of electron beam–irradiated high-density polyethylene/ethylene propylene rubber nanocomposite for shoe soles. These irradiated nanocomposites are melt blended before compression moulding of the specimens. The specimens were then irradiated under electron beams at 100 kGy. The irradiated nanocomposites were tested for their tensile, impact, hardness and wear properties. The morphology of the tensile failure fracture was analysed under a field emission scanning electron microscope. The addition of carbon nanotubes improved the mechanical properties of the samples for both unirradiated and irradiated nanocomposites; however, they dropped after 3 wt% of carbon nanotube content. The carbon nanotube content at 3 wt% was found to be the most effective in enhancing the mechanical properties, particularly wear in irradiated nanocomposite, due to the better crosslinking and carbon nanotube dispersion

Controlling the growth of vertically aligned single walled carbon nanotubes from ethanol for electrochemical supercapacitor application

Here, we report on the growth of VA-SWCNTs using the ACCVD technique. Al2O3-supported Co catalyst and high purity ethanol (carbon feedstock) were used for the growth process. Both Al layer and Co thin-films were deposited using an electron beam evaporator. The Al layer of 20 nm nominal thickness was manually oxidized before the deposition of 0.5 nm Co. The CNT growth was optimized using Si/SiO2 substrates, and the selected growth parameter was applied to each conducting substrate such as Inconel 600, Inconel 601, Si, and SUS 310S. In order to understand the mechanism of the CNT growth, synthesis of the catalyst nanoparticles and their structural characterization before CVD growth were carried out using atomic force microscope (AFM), scanning electron microscope (SEM), and x-ray diffraction (XRD). The properties of the as-grown CNTs were mainly characterized using Raman spectroscopy and SEM

Morphology and Electrical Characteristics of Single-Walled Carbon Nanotubes Film Prepared by Air Brush Technique

This study is to investigate the morphology and electrical characteristics of single-wall carbon nanotubes (SWCNTs) thin film deposition using air brush technique. A deposition setup consisting of a conventional artist air brush was developed and used to deposit SWCNT thin films and therefore the resulting film’s characteristics need to be investigated to gauge its suitability in producing uniform monolayer. The SWCNTs used were synthesized via Direct Injection Pyrolytic Synthesis (DIPS) method, with diameters ranging from 0.8 to 3 nm. The substrate was deposited using an airbrush with varying nozzle to study its effect to the resulting SWCNTs thin films’ characteristics. Subsequently, scanning electron microscope (SEM) were used to inspect the morphology and surface topography, and followed by preliminary electrical measurements. The result shows that good dispersion promotes uniform distribution of SWCNTs over large area of glass substrate. Moreover, the electrical measurement revealed that at 1 V, best morphology produced highest current at a nozzle height of 10 mm (15.3 µA) and the lowest current at a nozzle height of 4 mm (3.24 µA). From the results presented, it is demonstrated that conventional artist airbrush setup can be effectively used to deposit monolayer thin film of SWCNT with high degree of uniformity. This research is necessary for the process of depositing-controlled CNT thin film network, which can influence the material characteristics and performance of the variety of CNT-based device applications

Recent progress on fabrication of zinc oxide nanorod-based field effect transistor biosensors

Zinc oxide is a unique n-type semiconducting material, owing to wide bandgap of ~3.37 eV, non-toxic, bio-safe and biocompatible with high isoelectric point of ~9.5, make it as promising biomaterial to be utilized as sensing matrix in biosensor applications. In addition, ZnO that possess high electron affinity provide a good conduction pathway for the electrons hence result in significant electrical signal change upon detection to target biomolecules. Moreover, high surface area of ZnO nanorod enhance immobilization of enzymes, hence, increase the device performance. Field effect transistor (FET)-based biosensor offer simplicity in handling and label-free, has also become research topic among researchers for novel biosensor development. This review aims to explore the preparation of ZnO nanorod using hydrothermal method and investigate the fabrication of ZnO nanorod-based FET biosensor. Thus, contribute to enhance understanding towards biosensor development for health monitoring, especially based on FETs structure devices

Dilute electrodeposition of TiO2 and ZnO thin film memristors on Cu substrate

Memristor has become one of the alternatives to replace the current memory technologies. Fabrication of titanium dioxide, TiO2 memristor has been extensively studied by using various deposition methods. However, recently more researches have been done to explore the compatibility of other transition metal oxide, TMO such as zinc oxide, ZnO to be used as the active layer of the memristor. This paper highlights the simple and easy-control electrodeposition to deposit titanium, Ti and zinc, Zn thin film at room temperature and subsequent thermal oxidation at 600 oC. Gold, Au was then sputtered as top electrode to create metal-insulator-metal, MIM sandwich of Au/TiO2-Cu2O-CuO/Cu and Au/ZnO-Cu2O-CuO/Cu memristors. The structural, morphological and memristive properties were characterized using Field Emission Scanning Electron Microscopy, FESEM, X-Ray Diffraction, XRD and current-voltage, I-V measurement. Both Au/TiO2-Cu2O-CuO/Cu and Au/ZnO-Cu2O-CuO/Cu memristivity were identified by the pinched hysteresis loop with resistive ratio of 1.2 and 1.08 respectively. Empirical study on diffusivity of Ti4+, Zn2+ and O2- ions in both metal oxides show that the metal vacancies were formed, thus giving rise to its memristivity. The electrodeposited Au/TiO2-Cu2OCuO/Cu and Au/ZnO-Cu2O-CuO/Cu memristors demonstrate comparable performances to previous studies using other methods

Peranti suis nanoelektromekanikal (NEM) berunsurkan grafin dan tiub nano karbon (CNT)

Suis nanoelektromekanikal (NEM) mempunyai persamaan dengan suis konvensional semikonduktor apabila digunakan sebagai transistor dan penderia walaupun prinsip operasinya berbeza. Perbezaan prinsip operasi suis ini memberikan kelebihan kepada suis NEM untuk beroperasi dalam persekitaran yang melampau manakala suis konvensional semikonduktor mempunyai kelebihan daripada segi infrastruktur fabrikasi yang canggih. Dalam kertas ini, kami mengulas kemajuan terbaru dan potensi teknologi NEM dalam aplikasi pensuisan berdasarkan bahan berasaskan karbon seperti CNT dan grafin. Kemajuan reka bentuk geometri suis NEM seperti struktur rusuk berlubang, mempunyai kelebihan daripada segi voltan operasi peranti yang rendah, turut dibincangkan dalam kertas ini. Berdasarkan Kitaran Gemburan Gartner, teknologi, proses dan produk untuk suis NEM atau hibrid NEM-CMOS berada di takuk berbeza iaitu di jurang ilusi, cerun pencerahan dan dataran tinggi produktiviti. Kemudian, reka bentuk geometri suis NEM berasaskan bahan-bahan ini diulas dengan lengkap berdasarkan kajian kepustakaan terbaru. Kami mengenal pasti cabaran yang terlibat dalam proses fabrikasi suis NEM berasaskan CNT dan grafin seperti kebocoran get dan proses litografi yang mencabar. Kesimpulannya, kami meringkaskan kertas kajian ini kepada beberapa sudut perspektif, pandangan dan peluang pada masa depan dalam teknologi suis NEM

Characterization of graphene based capacitive microphone

This research focuses on the design, fabrication and characterization of the graphene based capacitive microphone. Finite element analysis (FEA) is first simulated in order to design and study the proposed graphene based capacitive microphone. While the fabrication introduced MEMS technique in order to reduce the physical size, volume and cost without neglecting the performance. This study discusses on physical characteristics of graphene diaphragm for capacitive microphone. The fabrication of 200 nm air gap and the free-standing suspended graphene with the contribution of the van der Waals force between the graphene layer as a diaphragm and the substrate are presented in this study. The first stage involved in this study was the photolithography process of patterning electrodes with 4 different dimensions of diaphragm. The characterization was performed by using surface profilometer, optical microscopy, Raman spectroscopy and FESEM to evaluate the physical characteristics of the diaphragm. In the last stage, LCR meter was used to measure the capacitive change with different diameter of graphene diaphragm within frequency range of 20 Hz to 20 kHz. FEA analysis showed the good sensitivity against the frequency response for the largest proposed diameter of diaphragm

Fabrication of flexible Au/ZnO/ITO/PET memristor using dilute electrodeposition method

DRAM has been approaching its maximum physical limit due to the demand of smaller size and higher capacity memory resistor. The researchers have discovered the abilities of a memristor, a Non Volatile Memory (NVM) that could overcome the size and capacity obstacles. This paper discussed about the deposition of zinc oxide (ZnO) on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrate by electrodeposition. Metallic Zn film was deposited on substrates with varying deposition time from 15 to 120 seconds in very dilute zinc chloride (ZnCl2) aqueous and subsequently oxidized at 150C to form ZnO/ITO coated PET junction. The deposited thin film was characterized via x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results from I-V measurement show the deposited ZnO exhibits pinched hysteresis loop. The hysteresis loop becomes smaller with increasing deposition time. The 15 seconds electrodeposition gave the largest hysteresis loop and largest value of resistive switching ratio of 1.067. The result of the synthesized ZnO on the flexible substrate can be one of the alternatives to replace the current memory system as the flexible memory system

Interdigitated MEMS Supercapacitor for Powering Heart Pacemaker

Power MEMS can be defined as microelectromechanical systems for power generation and energy conversion. Energy harvesting has become an increasingly popular option for powering electronic devices as a long-lasting power source. Energy scavenging is defined as the process by which the energy is derived such as vibration, solar, wind, and thermal. Energy harvesting from the environment can prolong the life cycle and reduce the maintenance costs of electronic devices. Among the various sources of energy storage, Among the various of energy storage, supercapacitor has recently gained much interest in fields such as bioMEMS, biomedical implants and power electronic devices due to its advantages such as high power density, rapid charge and discharge and unlimited number of recharge cycles. In biomedical and bioMEMS systems, an energy storage device is needed to power other active biomedical devices within the system. For implantable devices such as a heart pacemaker, the power requirement is in the range of 30–100 μW. Microsupercapacitors play an important role in energy harvesting system, such as collecting energy from ambient energy sources. Human body is very resourceful in generating micropower in the form of heat dissipation, deformation of elastic tissue, and motion. Due to the advantages of MEMS energy harvesting system, the system can be use widely for biomedical implant devices, such as heart pacemakers and hearing aids, and can be used for a long time and without the need for battery replacement. In this work, planar and double-stacked interdigital electrode supercapacitor designs were modeled using Coventorware software. From simulation, it is observed that for planar structure, the specific capacitance is 0.22 mF/cm−2, and for double-stacked structure specific capacitance can be increased to 0.48 mF/cm−2. In terms of specific power, the planar structure produces 0.99 mW/cm−2, and the double-stacked structure produces 2.18 mW/cm−2. These results highlight the superiority of the double-stacked MEMS interdigital supercapacitor design compared with its planar counterpart in terms of charging capacity and electrical performance, thus making it favorable for powering heart pacemaker