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In this paper, the interaction between florasulam (FU, 2',6',8-trifluoro-5-methoxy [Kragh-Hansen U, Molecular aspects of ligand binding to serum albumin. Pharmacol Rev 33(1):17-53 1981; Carter DC and Ho JX, Structure of serum albumin. Adv Protein Chem 45:153-203 1994; He XM, and Carter DC, Atomic structure and chemistry of human serum albumin. Nature 358(6383):209-215 1992] triazolo [1,5-c]pyrimidine-2-sulfonanilide) and bovine serum albumin (BSA) was investigated by fluorescence, ultraviolet absorption (UV) and Far-UV circular dichroism (CD) spectrometries. A strong fluorescence quenching was observed and the quenching mechanism was considered as static quenching. The binding constant of FU with BSA at 299 and 309 K were obtained as 1.5 x 10(4) and 7.1 x 10(3) l mol(-1), respectively. There was one binding site between FU and BSA. The thermodynamic parameters enthalpy change (DeltaH) and entropy change (DeltaS) were calculated as -57.89 kJ mol(-1) and -113.6 J mol(-1) K(-1), respectively, which indicated that the acting force between FU and BSA was mainly hydrogen bond and Van der Waals force. According to the Förster non-radiation energy transfer theory, the average binding distance between donor (BSA) and acceptor (FU) was obtained (r = 1.59 nm). The investigations of the UV/Vis and CD spectra of the system showed that the conformation of BSA was changed in presence of FU.

In this paper, we report MOS heterostructures grown by molecular beam epitaxy on III-V substrates, employing a high-κ dielectric stack comprised of gallium oxide and gadolinium gallium oxide. Mobilities exceeding 12,000 and 6,000 cm2/Vs, for sheet carrier concentration ns of about 2.5x1012 cm-2 were measured on MOSFET structures on InP and GaAs substrates, respectively. These structures were designed for enhancement mode operation and include a 10 nm thick strained InGa1-xAs channel layer with In mole fraction x of 0.3 and 0.75 on GaAs and InP substrates, respectively.

The performance of 300 nm, 500 nm and 1 mum metal gate, implant free, enhancement mode III-V MOSFETs are reported. Devices are realised using a 10 nm MBE grown Ga2O3/(GaxGd1-x)2O3 high-kappa (kappa=20) dielectric stack grown upon a delta-doped AlGaAs/InGaAs/AlGaAs/GaAs heterostructure. Enhancement mode operation is maintained across the three reported gate lengths with a reduction in threshold voltage from 0.26 V to 0.08 V as the gate dimension is reduced from 1 mum to 300 nm. An increase in transconductance is also observed with reduced gate dimension. Maximum drain current of 420 muA/mum and extrinsic transconductance of 400 muS/mum are obtained from these devices. Gate leakage current of less than 100 pA and subthreshold slope of 90 mV/decade were obtained for all gate lengths. These are believed to be the highest performance sub-micron enhancement mode III-V MOSFETs reported to date.

Developments over the last 15 years in the areas of materials and devices have finally delivered competitive III-V MOSFETs with high mobility channels. This paper briefly reviews the above developments, discusses properties of the GdGaO/ Ga2O3 MOS systems, presents GaAs MOSFET DC and RF data, and concludes with an outlook for high indium content channel MOSFETs. GaAs based MOSFETs are potentially suitable for RF power amplification, switching, and front-end integration in mobile and wireless applications while MOSFETs with high indium content channels are of interest for future CMOS applications.

We have developed scanning thermal microscopy probes for high resolution analysis of thermal properties in an atomic force microscope (AFM). Electron beam lithography and silicon micromachining have been used to batch fabricate Au/Pd thermocouples situated at the end of Si3N4 cantilevers. The cantilevers are patterned on the side of traditional style pyramidal AFM tips, giving a new shape of probe which is favorable for access to specimens containing significant topographic variation. Tip radius is approximately 50 nm and the probe has a macroscopic opening angle of 70°. The probes were scanned in the repulsive mode using a conventional AFM. Force feedback was optically employed to give topographic and thermal maps simultaneously by maintaining a constant force of approximately 5 nN. During initial scans using a photothermal test specimen, 80 nm period metal gratings were thermally resolved.

The key elements of a scanning near field microscope (SNOM) are high throughput and good spatial resolution. While both are desirable they are difficult to combine in a probe that is reproducible and durable. A batch‐fabrication method is being developed for AFM based SNOM with lithographically defined structured apertures. Due to the lithographic control of aperture size and shape the probes can be optimised for the imaging of sub‐wavelength structures, for spectroscopic analysis, fluorescence or polarisation measurements.

This paper presents a low damage inductively coupled plasma (ICP) etching process to define sub-100 nm platinum gate lines for III–V metal–oxide–semiconductor field-effect transistors (MOSFETs) fabrication. In this process, a negative resist etching mask patterned by electron beam lithography is used to define the high resolution platinum features using a combination of SF6 and C4F8 etch gases. Systematic investigation of the impact of various etch conditions, such as coil and platen power, gas composition, chamber pressure on etch rate and profile, resulted in a controllable etching process. Optical emission spectra of the ICP plasma have been checked for better understanding the etching mechanism. Etch induced damage of the underlying device channel of the III–V MOSFET materials has been evaluated through monitoring the sheet resistance variation of the materials at room temperature, which showed the process does not significantly degrade the electrical properties of the underlying device channel under optimized conditions.

A simple method is reported for fabrication of AlN/GaN MOS-HEMTs. Ultra-thin Al 2 O 3 , which is formed using thermal oxidation of evaporated Al, was used for surface passivation and as a gate dielectric. Prior to formation of Al 2 O 3 , the Al protects the very sensitive AlN epilayer from exposure to processing liquid chemicals. Fabricated two-finger AlN/GaN MOS-HEMTs with 3 m gate length and 200 m gate width showed good gate control of drain currents up to a gate bias of 3 V and achieved a maximum drain current, I DSmax , of ~900~mA/mm. The peak extrinsic transconductance, G max , of the device is ~100~mS/mm at V DS = 8=V. Capacitance-voltage ( C - V ) characteristics of Al 2 O 3 /AlN/GaN circular test MOS structures were observed and measured. They exhibited no hysteresis, indicating the good quality of the thermally grown Al 2 O 3 for realising AlN/GaN MOS-HEMTs for high power and high frequency applications.

To address issues associated with continual scaling of the International Technology Roadmap for Semiconductors (ITRS) [1] to follow Moore's Law, MOSFETs with high mobility channel materials are now being seriously considered. As a result, there has been a significant expansion in research into III-V MOSFETs as a potential n-channel device solution. For ultimate CMOS exploitation, self-aligned III-V MOSFETs with sub-20 nm critical dimensions will have to be realized using silicon compatible process flows. This paper reviews the current status of III-V MOSFET research from the perspective of silicon ULSI process compatibility.

This article describes a process flow that has enabled the first demonstration of functional, fully self-aligned 100nm enhancement mode GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) with GaxGdyOz as high-κ dielectric, Pt∕W as metal gate stack, and SiN as sidewall spacers. The flow uses blanket metal and dielectric deposition and low damage dry etch modules. As a consequence, no critical dimension lift-off processes are required. Encouraging data are presented for 100nm gate length devices including threshold voltage of 0.32V, making these the shortest, fully self-aligned gate length enhancement mode III-V MOSFETs reported to date. This work is a significant step forward to the demonstration of high performance “siliconlike” III-V MOSFETs.

The first demonstration of implant-free, flatband-mode In 0.75 Ga 0.25 As channel n-MOSFETs is reported. These 1 mum gate length MOSFETs, fabricated on a structure with average mobility of 7720 cm /Vs and sheet carrier concentration of 3.3 times 10 cm -2 , utilise a Pt gate, a high-k dielectric (k sime 20), and a delta-doped InAlAs/InGaAs/InAlAs heterostructure. The devices have a typical maximum drive current (I d,sat ) of 933 muA/mum, extrinsic transconductance (g m ) of 737 muS/mum, gate leakage (I g ) of 40 pA, and on-resistance (R on ) of 555 Omega .mum. The g m and R on figures of merit are the best reported to date for any III-V MOSFET.

Data is reported from 180 nm gate length GaAs n-MOSFETs with drive current (Ids,sat) of 386 µA/µm (Vg=Vd=1.5 V), extrinsic transconductance (gm) of 426 µS/µm, gate leakage ( jg,limit) of 44 nA/cm2, and on resistance (Ron) of 1640 Ω µm. The gm and Ron metrics are the best values reported to date for III–V MOSFETs, and indicate their potential for scaling to deca-nanometre dimensions.

In this study, we investigate in situ optical emission spectra from plasma in the reactive ion etching (RIE) of tungsten, a suitable candidate for gate metallization in compound-semiconductor-based high-mobility channel devices. This results in a detailed understanding of the effects of etching parameters vital to reducing etch induced damage and improving etching performance. A SF6 based chemistry was used with other functional gases, such as N2, O2, and CHF3. Van de Pauw (VdP) structures on GaAs based high electron mobility transistor (HEMT) layer structures were used for evaluating plasma-induced damage in the RIE process. The optimised process results in a maximum increase of 15% in the sheet resistance of the semiconductor material. Etched tungsten line widths down to 25 nm with well controlled profile were obtained by adjusting the etching conditions based on the understanding of the etching mechanism.

A novel room-temperature inductively coupled plasma chemical vapour deposition (ICP–CVD) technique has been developed, which yielded high-quality silicon nitride (SiN) films with a hydrogen content of less than 3 at. %. The chemical composition and bonding of the films were analysed by energy dispersive X-ray (EDX) analysis, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The film optical indexes measured by ellipsometry were well correlated with film composition. Very little plasma-induced damage was observed on Van de Pauw samples of GaAs-based high-electron-mobility transistor (HEMT) layer structures grown by molecular beam epitaxy (MBE). Breakdown electric field >4×106 V cm-1 was observed for an ultrathin 5 nm room-temperature-grown ICP–CVD SiN film embedded in a metal-insulator-metal (MIM) capacitor structure. This technique has been successfully incorporated into the III–V MMIC process flow to provide significant flexibility towards realising array-based MMICs.

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This article investigates sputter-induced damage caused by direct current magnetron sputter coating of tungsten on GaAs based high electron mobility transistor layer structures with channels buried less than 20nm from the surface. Van der Pauw structures were used to study the effect of tungsten sputtering on the transport properties of these shallow channels. Using this approach we established that substrate damage can be minimized by using low sputtering currents, a large source to substrate distance, and a high sputtering pressure. Unfortunately such sputtering conditions do not produce the best quality dense films necessary for device fabrication and it was necessary to establish conditions which were a compromise of film quality and substrate damage. Postsputter annealing was found to significantly reduce the damage and a loss of 10% in semiconductor conductivity was obtained for good quality tungsten films.

The combination of direct-write electron beam lithography and bulk silicon micromachining is shown to give great flexibility in the definition of nanosensors. The technique is based on a novel method for coating the specimen with electron beam resist allowing high resolution features to be defined on the top of micromachined asperities or in 200 μm deep etched holes. Examples of sensors fabricated using this method include advanced magnetic nanosensors such as Hall probe sensors, electromagnetic coils or combined coils and Hall probes. Near-field optical atomic force microscope probes are demonstrated with reproducible aperture size down to 20×35 nm. Near-field optical probes using a shaped aperture to allow the passage of linearly polarized light are shown to offer optical throughputs up to 2% with modest collection optics. The use of a near-field optical probe having a crossed slit form is demonstrated to give high throughput and resolution in two dimensions for the imaging of fluorescent objects. Near-...

We have developed novel probes which allow scanning near-field optical microscopy to be performed in a conventional atomic force microscope(AFM). Direct-write electron-beam lithography and siliconmicromachining have been used in a reliable batch process which allows the production of many probes at once without resort to handicraft. The aperture is situated at the hollow tip apex of a conventional silicon nitrideAFM cantilever. Since there is no waveguide cutoff, the overall light throughput is dramatically enhanced. The integration of a conventional force microscope cantilever with the aperture allows more reliable and better control of the aperture-sample distance than that obtained by “shear-force” detection. In addition, since the apertures are defined by lithographic means, the size and shape of apertures are well controlled and reproducible. We present the first results of near-field optical imaging and luminescence imaging using these probes demonstrating excellent light throughput and also good spatial and spectral resolution.

We present a novel method for the fabrication of generic scanned-probe microscope probes by performing multiple level direct-write electron-beam lithography on the apex of micromachined atomic force microscope tips. Pattern transfer is by conventional etching or liftoff in a wide range of materials. Lithographic resolution is 50 nm or better. The substrates support the use of automatic alignment and allow for the fabrication of 50 probes/in2. The integration of a force-sensing cantilever permits simple height regulation of the probes during operation. The technology is illustrated by the fabrication of thermocouple and near-field optical probes.

The California Department of Transportation (Caltrans) has been using scrap tire rubber in asphalt pavements since the 1970s in chip seals and the 1980s in rubberized hot mix asphalt(RHMA). Both the wet (field blend) and dry processes were used in early trials. Caltrans has also used rubber modified binders containing both crumb rubber modifier and polymer modifier that could be manufactured at a refinery facility, a terminal blend wet process. Since the beginning of this century, Caltrans increased the use of scrap tire rubber in paving projects and invested considerable resources in developing technically sound, cost effective, and environmentally friendly strategies for using scrap tire rubber in roadway applications. By the end of year 2010, approximately 31 % of all hot mix asphalt (HMA) placed by Caltrans was rubberized HMA, roughly 1.2 million tons. Caltrans efforts in using asphalt rubber products were also demonstrated in its research and technology development. These included the construction of two full-scale field experiments, five warranty projects, and an accelerated pavement study using a heavy vehicle simulator. Additionally, terminal blend asphalt rubber and rubberized warm mix asphalts began to be experimented on trial basis. This paper provides a comprehensive review of Caltrans experience over four decades with asphalt rubber products. Current practices and future outlook are also discussed.

This paper presents a series of monolithic microwave integrated circuit (MMIC) resonant tunneling diode (RTD) oscillators. The oscillator circuit topology employs two InGaAs/AlAs RTDs in parallel and each device is biased individually. The oscillators operate at 125/156/206/308 GHz with -1.7/-3.3/-14.6/-4.8 dBm output power. With improved epitaxial layer structures and oscillator designs, it is expected that the output power will reach several milliwatts. This work shows the promising potential of RTD oscillators as terahertz (THz) sources for high speed wireless communications, etc.

This paper presents monolithic microwave integrated circuit (MMIC) resonant tunneling diode (RTD) oscillator with high performance: high power at high frequencies. The circuit topology employs two In0.53Ga0.47As/AlAs RTDs in parallel and each device is biased individually. These oscillators operate at 125GHz, 156GHz and 166 GHz with output power 0.34 mW, 0.24 mW and 0.17 mW respectively. These are highest power reported for RTD oscillators in D-band (110 GHz-170 GHz) frequency range. The phase noise of the RTD oscillators was characterized and is reported. This work demonstrates the circuit-based RTD oscillator design approach to increase the output power of RTD oscillators at millimeter-waves.