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Clinical implementation of MOSFETs for entrance dose in-vitro dosimetry with high energy photons for external beam radiation therapyMorton, Jason January 2006 (has links)
In external beam radiotherapy quality assurance is carried out on the individual components of the treatment chain. The patient simulating device, planning system and linear accelerators are tested regularly according to set protocols developed by national and international organizations. Even though these individual systems are tested errors can be made in the transfer between systems. The best quality assurance for the system is at the end of the treatment planning chain. In-vivo dosimetry measures the dose to the target volume through indirect measures at the end of the treatment planning chain and is therefore the most likely method for picking up errors which might occur earlier in the chain. Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) have been shown to have a similar error in estimating entrance dose for in-vivo dosimetry to diodes, but no studies have been done clinically with entrance dose in-vivo dosimetry with MOSFETs. The time savings for using MOSFETs makes them preferable to TLD's. Due to their small size and versatility in other applications they are useful as more than dedicated in-vivo dosimetry systems using diodes. Clinical implementation of external beam in-vivo dosimetry would add another use to the MOSFETs without purchasing more specialized equipment. My studies have shown that MOSFETs can be used clinically for external beam in-vivo dosimetry using entrance dose measurements. After the MOSFET measurement system was implemented using a custom built aluminium build up cap clinical measurements were performed. A total of 23 patients and 54 fields were studied. The mean for all clinical measurements was 1.3 %, with a standard deviation of 2.6 %. Results were normally distributed around a mean with skewness and kurtosis as -0.39 and 0.34 respectively. For breasts the mean was 1.8 %, with a standard deviation of 2.7 %. For prostates and hips the mean was 1.3 % with a standard deviation of 2.9 %. These results are similar to studies conducted with diodes and TLD's. From these results one can conclude that MOSFETs can be used for entrance dose in-vivo dosimetry and are no worse than diodes or TLD's in terms of their measurement accuracy. / Thesis (M.Sc.)--School of Chemistry and Physics, 2006.
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Mobility enhancement for organic thin-film transistors using nitridation methodKwan, Man-chi. January 2006 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
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Electrolyte-Based Organic Electronic DevicesSaid, Elias January 2007 (has links)
<p>The discovery of semi-conducting and conducting organic materials has opened new possibilities for electronic devices and systems. Applications, previously unattainable for conventional electronics, have become possible thanks to the development of conjugated polymers. Conjugated polymers that are both ion- and electron conducting, allow for electrochemical doping and de-doping via reversible processes as long as both forms of conduction remain available. Doping causes rearrangement of the -system along the polymer backbone, and creates new states in the optical band gap, resulting in an increased electronic conductivity and also control of the color (electrochromism). Doping can also occur by charge injection at a metal – semiconducting polymer interface. Electrochemical electronic devices and solid state devices based on these two types of doping are now beginning to enter the market.</p><p>This thesis deals with organic based-devices whose working mechanism involves electrolytes. After describing the properties of conjugated polymers, fundamentals on electrolytes (ionic conductivity, types, electric double layer and the electric field distribution) are briefly presented. Thereafter, a short review of the field of organic field effect transistors as well as a description of transistors that are gated via an electrolyte will be reviewed.</p><p>Paper I present a novel technique to visualize the electric field within a two-dimensional electrolyte by applying the electrolyte over an array of electronically isolated islands of electrochromic polymer material on a plastic foil. By observing the color change within each polymer island the direction and the magnitude of the electric field can be measured. This technology has applications in electrolyte evaluation and is also applicable in bio-analytical measurements, including electrophoresis. The focus of paper II lies on gating an organic field effect transistor (OFET) by a polyanionic proton conductor. The large capacitance of the electric double layer (EDL) that is formed at organic semiconductor/polyelectrolyte upon applying a potential to the gate, results in low operation voltages and fast response. This type of transistor that is gated via electric double layer capacitor is called EDLC-OFET. Because an electrolyte is used as a gate insulator, the role of the ionic conductivity of the electrolyte is considered in paper III. The effect on the electronic performance of the transistor is studied as well by varying the humidity level.</p>
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Characterization of solution-based inorganic semiconductor and dielectric materials for inkjet printed electronicsMunsee, Craig L. 14 June 2005 (has links)
The long-term goal of this research project is the development of solution-based
inorganic dielectric and semiconductor materials for inkjet printed electronics.
The main focus of this thesis involves testing of the materials and devices
under development.
A new solution-based inorganic dielectric material (HfOSO₄), given the
name hafsox, is developed and shows excellent dielectric properties. Hafsox with
the addition of lanthanum, to improve film dehydration, has successfully been
demonstrated as a gate dielectric. Metal-insulator-metal (MIM) capacitance testing
of hafsox with lanthanum, has resulted in a low loss tangent of 0.30% at 1
kHz, a relative permittivity of 11.47 at 1 kHz, a breakdown voltage of 6.30 MV
cm⁻¹, and a leakage current density of 4.38 nA cm⁻² at 1 MV cm⁻¹.
Progress has also been achieved in the development of solution-based semiconductor
materials. To date the most successful of these materials is zinc indium
oxide (ZIO), which has been demonstrated as a thin-film-transistor (TFT) channel
material. This ZIO TFT is a depletion-mode device with a turn-on-voltage
of V[subscript on]~ -19 V, a threshold voltage of V[subscript T] ~-16 V, and a drain current on-to-off
ratio of ~10³. Mobilities extracted from this ZIO TFT include an incremental
mobility of μ[subscript inc] ~0.05 cm² V⁻' sec⁻', an effective mobility of μ[subscript eff] ~0.02 cm²
V⁻' sec⁻', and an average mobility of μ[subscript avg] ~0.02 cm² V⁻' sec⁻' at V[subscript GS]=20 V.
The development of metal-semiconductor field-effect transistors (MESFET)
TFTs is also investigated as a means of eliminating the need for a dielectric
material in order to reduce the complexity of fabricating circuits. MESFETs are
attempted with semiconductor materials such as CdS that is deposited by chemical
bath deposition (CBD) and SnO₂ that is deposited by RF magnetron sputtering,
but with little success. The most successful MESFET-like device fabricated, employing
SnO₂ as the channel material, is a strong depletion-mode device with a
small amount of gate voltage modulation. / Graduation date: 2006
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Radiation effects on III-V heterostructure devicesJun, Bongim 01 July 2002 (has links)
The neutron and electron radiation effects in Ill-V compound semiconductor
heterostructure devices are studied in this thesis. Three types of devices
investigated are AlGaAs/GaAs high electron mobility transistors (HEMTs),
AlGaAs/InGaAs/GaAs heterostructure insulated gate field effect transistors
(HIGFETs), and InP/InCaAs/InGaAs single heterojunction bipolar transistors
(SHBTs). HEMTs and HIGFETs are primarily investigated for neutron
irradiation effects. Detailed optimized processing of HEMT devices is introduced.
Numerical as well as analytical models that incorporate radiation
induced degradation effects in HEMTs and HIGFETs are developed.
The most prominent radiation effects appearing on both HEMT and HIGFET
devices are increase of threshold voltage (V[subscript T]) and decrease of transconductance
(g[subscript m]) as radiation dose increases. These effects are responsible for drain current
degradation under given bias conditions after irradiation. From our experimental
neutron irradiation study and our theoretical models, we concluded that
threshold voltage increase is due to the radiation-induced acceptor-like (negatively
charged) traps in the GaAs channel region removing carriers. The mobility
degradation in the channel is responsible for g[subscript m] decrease. Series resistance
increase is also related to carrier removal and mobility degradation. Traps introduced
in the GaAs region affect the device performance more than the traps
in the AlGaAs doped region. V[subscript T] and g[subscript m] of HIGFET devices are less affected
by neutron radiation than they are in HEMTs. This difference is attributed to
different shapes of the quantum well in the two devices.
The main effects of electron and neutron irradiation of SHBTs are decrease
of collector current (I[subscript c]), decrease of common-emitter DC gain, increase of the
collector output conductance (��I[subscript c]/��V[subscript CE]), and increase of collector-collector
offset voltage. The decrease of breakdown voltage of reverse biased base-emitter
junction diode is responsible for increasing the output conductance after irradiation.
Base-collector junction degradation also induces collector-emitter offset
voltage increase. / Graduation date: 2003
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SPICE models for flicker noise in p-MOSFET's and phase noise effects on oscillator circuitsZhou, Junlin, 1973- 12 June 2000 (has links)
Graduation date: 2001
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Comparison of carbon nanotube and graphene field-effect transistor biosensorsSaltzgaber, Grant William 19 September 2012 (has links)
Detection of biomolecules is important for the diagnosis and treatment of diseases. Low concentration detection, specific biomolecule detection, and point-of-care use are appealing characteristics for biosensors because of the possibility of early detection and quick results of specific biomolecules. Furthermore, inexpensive biosensors are appealing so that they are accessible to the general population. The biosensors in this study have the potential to satisfy these characteristics.
In this study graphene field-effect transistors (G-FET) were fabricated. Graphene was grown using chemical vapor deposition (CVD) and transferred to a silicon/silicon oxide substrate. The CVD method is the most scalable and cost-effective method of producing graphene for devices. Standard photolithography was used to pattern and then deposit metal electrodes. Two separate experiments were conducted; one using electrostatic attraction to bind protein to the active area of the G-FET to detect the protein poly-L-lysine (PLL) and one using an aptamer modified G-FET to selectively detect the protein thrombin. Analyte was delivered using a homebuilt, pressure driven, microfluidic, mass flow system.
Both experiments showed a detection of the protein. The PLL experiment showed a clear change in the effective gate voltage of the G-FET. The thrombin experiment showed a change in the effective gate voltage that varied with differing concentrations of thrombin present. Furthermore, in the thrombin experiment by changing from a thrombin solution back to buffer the effective gate voltage was brought back to its original value. A competing protein was introduced and gave a signal comparable to the signal of a 10 times smaller concentration of thrombin. All of this shows that CVD grown graphene in a FET biosensor can be used for protein detection. Furthermore, the specific detection of thrombin suggests that aptamer modified G-FETs with CVD grown graphene can be used as a protein specific biosensor. / Graduation date: 2013
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Growth and characterization of III-V compound semiconductor materials for use in novel MODFET structures and related devicesSchulte, Donald W. 27 November 1995 (has links)
Graduation date: 1996
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Noise measurements, models and analysis in GaAs MESFETs circuit designYan, Kai-tuan Kelvin 08 January 1996 (has links)
Graduation date: 1996
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Quantum-mechanical modeling of transport parameters for MOS devices /Höhr, Timm, January 2006 (has links)
Originally presented as the author's thesis (Swiss Federal Institute of Technology), Diss. ETH No. 16228. / Summary in German and English, text in English. Includes bibliographical references (p. 123-132).
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