Khairul Anuar Mohamad

n-Channel Organic Thin-Film Transistors based on Naphthalene–Bis(dicarboximide) Polymer for Organic Transistor Memory Using Hole-Acceptor Layer

An investigation of threshold voltage shifts in organic thin-film transistors (OTFTs) based on poly{[N,N″-bis(2-octyldodecyl)-naphthalene-1, 4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5″-(2,20-bithiophene)} [P(NDI2OD-T2)] with additional poly(3-hexylthiophene) (P3HT) films on a poly(methyl methacrylate) (PMMA) organic dielectric layer is reported. With a top source-drain contact structure, the device exhibited a unipolar property with n-channel characteristics similar to those of the P(NDI2OD-T2)-only device. Furthermore, the existence of P3HT films as hole acceptor-like storage layers resulted in reversible V th shift upon the application of external gate bias (V bias) for a certain bias time (T bias). Hence, the P(NDI2ODT2)/ P3HT-OTFTs exhibited a large memory window (I´V th = 10.7 V) for write and erase electrically without major degradation in saturation mobility [I¼ sat = (1.8-2.8) A— 10 ¯â�´ cm 2 V ¯¹ s ¯¹]. These results clearly indicate the utility of the naphthalene-bis(dicarboximide) (NDI)-based polymer-hole acceptor layer in the development of n-channel organic transistor memories.

Bias-Induced Threshold Voltage Shifts in Organic Thin-Film Transistors by Soluble Fullerene Layers on Gate Dielectric

An investigation of threshold voltage shifts in organic thin-film transistors (TFTs) based on pentacene with an additional soluble fullerene derivatives of [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) on gate dielectric. With an additional soluble fullerene layer, the threshold voltage (V(th)) is optimized from -3: 9 to -1:1 V without affect the mode operation of the devices, while retaining the carrier mobility (0.02-0.03 cm(2) V(-1) s(-1)) and on/off current ratio (similar to 10(4)). Furthermore, the existence of PCBM agglomerates as electron acceptor-like traps resulted in a shift of Vth in the positive and reversible directions depending on the magnitude of gate bias (V(bias)) as well as duration of time bias (T(bias)). The device operation changed into normally-on (depletion-accumulation) mode upon positive Vbias as the duration of Tbias was increased, which attributes to the formation of a conductive layer at the pentacene-fullerene interface. Moreover, the recovery of Vth was further enhanced by a high negative V(bias) for a short duration. In addition, the mobility was minimally affected by both Vbias conditions

Molecular Orientation of Poly(3-hexylthiophene)/Fullerene Composite Thin Films

Focused on the relationship between the molecular orientation and the electrical performance of poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester (P3HT/PCBM) composite thin films to elucidate the effect of changing amount of PCBM in P3HT:PCBM by weight ratio in organic solution has been studies. The P3HT/PCBM composite thin films were investigated by an electron spin resonance (ESR) and X-ray diffraction (XRD) to reveal the film molecular and structure orientation. It was observed that the composite films with a small amount of PCBM were capable of altering the molecular structure of P3HT. It was also observed that the presence of a small amount of PCBM molecules improved the device performance of P3HT thin film transistors (TFTs), which provide the mobility on the order of 10-3 cm2 V-1 s-1 with an on/off current ratio of 10-4. The threshold voltage was also higher than of pure P3HT TFTs.

Novel magnetic core materials impact modelling and analysis for minimization of RF heating loss

The eddy current that exists in RF transformer/inductor leads to generation of noise/heat in the circuit and ultimately reduces efficiency in RF system. Eddy current is generated in the magnetic core of the inductor/transformer largely determine the power loss for power transferring process. The losses for high-frequency magnetic components are complicated due to both the eddy current variation in magnetic core and copper windings reactance variation with frequency. Core materials permeability and permittivity are also related to variation of such losses those linked to the operating frequency. This paper will discuss mainly the selection of novel magnetic core materials for minimization of eddy power loss by using the approach of empirical equation and impedance plane simulation software TEDDY V1.2. By varying the operating frequency from 100 kHz to 1GHz and magnetic flux density from 0 to 2 Tesla, the eddy power loss is evaluated in our study. The Nano crystalline core material is found to be the best core material due to its low eddy power loss at low conductivity for optimum band of frequency application.

Model cart control using EMG signal

This paper describes the development of EMG signal acquisition system application for model cart control. The main application of this type of control is to assist disabled people or frail people to control a cart or device via their healthy muscle. In this project, the circuit was simulated, developed and troubleshoots. The aim of model cart control was to control four basic directions which is forward, backward, turn left and turn right. Threshold voltage level comparison method is used in this project for model cart control. By considering the user friendly issue for the application system, EMG signal acquisition method was decided to be used and obtained with surface electrode. There are two stages to be done for this system, in which the first stage is the signal acquisition system and the second stage is to control the action of model cart. First stage included pre-amplifier, rectification and filtering, which were done with instrumentation amplifier, active low pass and high pass filter and precision full wave rectifier. Second stage included the microcontroller and motor driver in which the microcontroller functions to read the two channel EMG signal and give signal for the motor driver to control the DC geared motor. The result of the hardware testing is compared with the software simulation where the same output is obtained. There were also some limitation and problem which have not been solved. There was wire connected to the model cart where it is not very convenient for the model cart to move around or further.

Fabrication and characterization of 6,13-bis(triisopropylsilylethynyl)-pentacene active semiconductor thin films prepared by flow-coating method

Investigation on the physical characterization and comparison of organic thin film based on a soluble 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene is reported. Oriented thin-films of pentacene have been successfully deposited by flow-coating method, in which the chloroform solution is sandwiched between a transparent substrate and a slide glass, followed by slow-drawing of the substrate with respect to the slide glass. Molecular orientation of flow-coated TIPS-pentacene is comparable to that of the thermal-evaporated pentacene thin film by the X-ray diffraction (XRD) results. XRD results showed that the morphology of flow-coated soluble pentacene is similar to that of the thermal-evaporated pentacene thin films in series of (00l) diffraction peaks where the (001) diffraction peaks are strongest in the nominally out-of-plane intensity and interplanar spacing located at approximately 2θ = 5.33° (d-spacing, d001 = 16 A). Following that, ITO/p-TIPS-pentacene/n-ZnO/Au vertical diode was fabricated. The ...

Poly(3-hexylthiophene)/Fullerene Organic Thin-Film Transistors: Investigation of Photoresponse and Memory Effects

Organic thin-film transistors (OTFTs) incorporating blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as an active layer were fabricated, and the photoresponse and memory effects of the P3HT/PCBM-TFTs were investigated. With top source–drain contact, the device exhibited a unipolar property with p-channel characteristics in dark condition. Upon illumination, a significant increase in the drain current was observed, and the transfer curve was shifted in the positive direction with ΔVth = 15.5 V. Moreover, the drain current increased gradually with the response time of light illumination, while it decreased gradually with delay time after turning off the light illumination. The memory effects of the P3HT/PCBM-TFTs were attributed to the slow relaxation of photoinduced charge carriers and the electron trapping–detrapping mechanism. The memory functions of program and erase can be performed using a combination of the optical response and gate voltages.

Conductance and Capacitance Responses of Metal-Organic-Metal Structure Based Organic Semiconductor Thin Film

In this work we have investigated the frequency and the bias voltage dependence of the electrical responses of organic structures based on poly (triarylamine) (PTAA) thin film using ITO/Organic/Al diode structure. The frequency-dependent and bias voltage-dependent conductance and capacitance were investigated using a precision LCR meter with wide frequency test (10 Hz – 100 kHz) and various bias voltages ranges (0.2 to 5.0 V), respectively. Investigation revealed that conductance was strongly dependent on the frequency and bias voltage-dependent. Conductance was inversely proportional to the capacitance among the frequency. Meanwhile, the capacitance and series resistance were dependent until a certain value at the low frequency region, but the capacitance and series resistance were independent at high frequencies.

Influence of substrate temperature and post annealing of CuGaO2 thin films on optical and structural properties

A transparent p-type thin film CuGaO2 was deposited by using RF sputtering deposition method on plastic (PET) and glass substrate. The characteristics of the film is investigated. The thin film was deposited at temperature range from 50-250°C and the pressure inside the chamber is 1.0×10−2 Torr and Argon gas was used as a working gas. The RF power is set to 100 W. The thickness of thin film is 300nm. In this experiment the transparency of the thin film is more than 70% for the visible light region. The band gap obtain is between 3.3 to 3.5 eV. The details of the results will be discussed in the conference.

Structural properties 3,16-bis triisopropylsilylethynyl (pentacene) (TIPS-pentacene) thin films onto organic dielectric layer using slide coating method

3,16-bis triisopropylsilylethynyl (Pentacene) (TIPS-Pentacene) compactable interface property is important in order to have a good arrangement of molecular structure. Comparison for TIPS-Pentacene deposited between two different surface layers conducted. 0.1wt% TIPS-Pentacene diluted in chloroform were deposited onto poly(methylmeaclyrate) (PMMA) layered transparent substrates using slide coating method. X-ray diffraction (XRD) used to determine crystallinity of thin films. Series of (00l) diffraction peaks obtained with sharp first peaks (001) for TIPS-Pentacene deposited onto PMMA layer at 5.35° and separation of 16.3 A. Morphology and surface roughness were carried out using scanning electron microscope (SEM) and surface profilemeter LS500, respectively.TIPS-Pentacene deposited onto PMMA layer formed needled-like-shape grains with 10.26 nm surface roughness. These properties were related as thin film formed and its surface roughness plays important role towards good mobility devices.