MOS Type Research Articles

ChemInform Abstract: A Comparison of Oxidation and Oxygen Substitution in MoS2 Solid Film Lubricants

Abstract Significant advancements in the production of low friction, long wear life, sputter-deposited MoS 2 lubricant coatings have been made in the last decade. The introduction of multi-layered coatings, the establishment of careful controls on doping during DC and magnetron sputter deposition, and the implementation of ion assisted deposition have resulted in lubricants with substantially longer wear lives (up to a factor of ten greater than in the early 1980s) and lower sliding friction coefficients. A major research effort, designed to improve the performance of solid lubricants, involved a number of laboratories during this time period, resulting in these major breakthroughs. However, even with this concentrated effort, the typical investigation involved making an educated guess, based on previous experience, of the deposition conditions, target compositions, or post treatments that might be expected to provide improved performance of resulting coatings. One notable discovery during this time period was that typical MoS 2 films contain large quantities (up to 20 atom %) of oxygen substituted for sulfur in individual crystal lattices. In this paper we will compare the effects of this oxygen substitution with the effects of oxidation which involves a change in the oxidation number of the central molybdenum atoms within the crystals. A discussion of the relationship(s) between chemistry and coating structure and tribological performance will be presented with emphasis on defect chemistry and multiple phase interactions. Speculations on the role of coating chemistry in determining coating performance in applications such as in ball bearings will be presented.

Gas sensor array system inspired on the sensory diversity and redundancy of the olfactory epithelium

This paper presents a chemical sensing system that takes inspiration from the combination of sensory diversity and redundancy at the olfactory epithelium to enhance the chemical information obtained from the odorants. The system is based on commercial MOS sensors and achieves, first, diversity trough different types of MOS along with modulation of their temperatures, and second redundancy including 12 MOS sensors for each type (12×8) combined with a high-speed multiplexing system that allows connecting 16 load resistors with each and every one of the 96 sensors in about two seconds. Exposition of the system to ethanol, ammonia, and acetone at different concentrations shows how the system is able to capture a large amount of information of the identity and the concentration of the odorant.

Green synthesis of metal sulfide nanocrystals through a general composite-surfactants-aided-solvothermal process

In this paper, we developed a generalized and greener composite-surfactants-assisted-solvothermal process (CSSP) to produce colloidal nanoparticles of metal sulfides. X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS) revealed that single-molecular-layer type of MoS 2 nanoparticles with diameter 6–10 nm were successfully synthesized. The molecular structure model of the capped MoS 2 nanoparticles was suggested through further examination by infrared spectra. Hexagonal CdS nanocrystals with spherical, triangle, and hollow sphere shapes were controllably synthesized by varying the experimental conditions. A possible in-situ reduction–sulfidation mechanism was proposed for the formation of Ag 2S nanocrystals, where the metal ions were reduced to metallic nanoparticles before the generation of sulfides. The obtained nanocrystals through this CSSP approach could provide the building blocks for the bottom-up approach to nanoscale fabrication in nanoscience and nanotechnology.

UHF 대역 모바일 RFID 시스템에 적합한 저잡음 콜피츠 VCO 설계

본 논문에서는 모바일 RFID 시스템 환경을 제시하였고, 그 환경에 적합한 저 잡음 차동 콜피츠 전압 제어 발진기를 구현하였다. 밀집 리더 환경에 맞춘 전압 제어 발진기는 <TEX>$0.35{\mu}m$</TEX> 공정을 사용하였고, 주파수 범위는 RFID 주파수 범위인 <TEX>$860{\sim}960 MHz$</TEX>를 포함시킬 수 있도록 <TEX>$1.55{sim}2.053 GHz$</TEX>로 설계하였다. 2분주기 출력에서 측정한 위상 잡음은 오프셋 주파수가 40 kHz일 때 -106 dBc/Hz로 측정되었고, 1MHz일 때에는 -135 dBc/Hz로 측정되었다. 5 비트의 디지털 튜닝을 이용하여 낮은 발진기 이득(<45 MHz/V)을 갖게 하여 주파수 합성기에서의 위상 잡음 특성을 좋게 하였다. 설계한 차동 콜피츠 발진기의 FOM은 1.93 dB로 타 2 GHz 대역의 발진기들 보다 높게 측정되었다. A regulated low phase noise differential colpitts VCO(Voltage Controlled Oscillator) for mobile RFID system is presented. The differential colpitts VCO meets the dense reader environment specifications. The VCO use a <TEX>$0.35{\mu}m$</TEX> technology and achieves tuning range <TEX>$1.55{sim}2.053 GHz$</TEX>. Measuring 910 MHz frequency divider output, phase noise performance is -106 dBcMz and -135dBc/Hz at 40 kHz and 1MHz offset, respectively. 5-bit digital coarse-tuning and accumulation type MOS varactors allow for 28.2% tuning range, which is required to cover the LO frequency range of a UHF Mobile RFID system, Optimum design techniques ensure low VCO gain(<45 MHz/V) for good interoperability with the frequency synthesizer. To the author' knowledge, this differential colpitts VCO achieves a figure of merit(FOM) of 1.93dB at 2-GHz band.

Bionanodot monolayer array fabrication for nonvolatile memory application

A polyelectrolyte thin film which was simply spin-coated on a substrate showed the high-density adsorption of bionanodot-accommodated ferritins through electrostatic interaction. Solution pH adjustment facilitated the control of adsorption density to a value grater than 80% of the theoretical maximum density. The formed polyelectrolyte film was very thin and vulnerable like protein, therefore, only the array with densely adsorbed bionanodot was left on the substrate after organic component removal. The floating nanodot gate type MOS capacitor fabricated with this bionanodot array showed a memory effect, and no negative influences of polymer such as carrier trapping on the capacitance-voltage characteristics was observed.

Highly reliable SiO2/SiN/SiO2(ONO) gate dielectric on 4H‐SiC

AbstractThe marked lack of long‐term reliability in thermal gate oxides has thwarted practical applications of SiC power MOS devices. Gate dielectrics with a SiO2/SiN/SiO2(ONO) structure have been studied and optimized on a commercial 4H‐SiC epitaxial substrate as a fundamental resolution to this problem. A medium charge‐to‐failure value of more than 400C/cm2 was achieved for polycrystalline gate MONOS capacitors with an equivalent SiO2 thickness of 40 nm and fabricated with a typical power MOS process. The medium time‐to‐failure at an operating field of 3 MV/cm was extrapolated to be over 2 million years at room temperature. An ONO gate dielectric DMOS was demonstrated to show stable normally‐off transistor operation on 4H‐SiC. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(5): 1– 10, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20329

Total Dose Radiation Response of Nitrided and Non-nitrided SiO$_{2}$/4H-SiC MOS Capacitors

The total dose radiation response of nitrided and non-nitrided n-type 4H-SiC is reported for metal oxide semiconductor capacitors exposed to 10-keV X-rays under positive bias. The radiation response is affected strongly by differences in the SiC band gap and interface/near interface SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> trap density from typical Si MOS devices. Significantly higher net trapped positive charge densities were observed in nitrided n-SiC MOS capacitors compared to the non-nitrided samples. The mechanisms contributing to the differences in the charge trapping in these devices are discussed. Differences in the interfacial layer between SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si and SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /SiC are responsible for the observed dissimilarities in charge trapping behavior

Asymmetric Interface Densities on n and p Type GaN MOS Capacitors

Both n-type and p-type GaN MOS capacitors with plasma-enhanced CVD-SiO2 as the gate oxide were characterized using both capacitance and conductance techniques. From a n type MOS capacitor, an interface state density of 3.8×1010/cm2-eV was estimated at 0.19eV near the conduction band and decreases deeper into the bandgap while from a p type MOS capacitor, an interface state density of 1.4×1011/cm2-eV 0.61eV above the valence band was estimated and decreases deeper into the bandgap. Unlike the symmetric interface state density distribution in Si, an asymmetric interface state density distribution with lower density near the conduction band and higher density near the valence band has been determined.

Charge transport along luminescent oxide layers containing Si and SiC nanoparticles

The electrical conductivity of silicon oxides containing silicon and silicon–carbon nanoparticles has been investigated. By use of sequential Si + and C + ion implantations in silicon oxide followed by an annealing at 1100 °C, luminescent Si nanocrystals and SiC nanoparticles were precipitated. The characterization of the electrical transport has been carried out on two kinds of structures, allowing parallel or perpendicular transport, with respect to the substrate. The first type of samples were elaborated by means of a focus-ion-beam technique: electrical contacts to embedded nanoparticles were made by milling two nanotrenches on the sample surface until reaching the buried layer, then filling them with tungsten. The distance between the electrodes is about 100 nm. The second type of samples correspond to 40 nm thick typical MOS capacitors. The electron transport along the buried layer has shown a dramatic lowering of the electrical current, up to five orders of magnitude, when applying a sequence of voltages. It has been related to a progressive charge retention inside the nanoparticles, which, on its turn, suppresses the electrical conduction along the layer. On the other hand, the MOS capacitors show a reversible carrier charge and discharge effect that limits the current at low voltage, mostly due to the presence of C in the layers. A typical Fowler–Nordheim injection takes place at higher applied voltages, with a threshold voltage equal to 23 V.

Radiation-induced off-state leakage current in commercial power MOSFETs

The total dose hardness of several commercial power MOSFET technologies is examined. After exposure to 20 krad(SiO/sub 2/) most of the n- and p-channel devices examined in this work show substantial (2 to 6 orders of magnitude) increases in off-state leakage current. For the n-channel devices, the increase in radiation-induced leakage current follows standard behavior for moderately thick gate oxides, i.e., the increase in leakage current is dominated by large negative threshold voltage shifts, which cause the transistor to be partially on even when no bias is applied to the gate electrode. N-channel devices biased during irradiation show a significantly larger leakage current increase than grounded devices. The increase in leakage current for the p-channel devices, however, was unexpected. For the p-channel devices, it is shown using electrical characterization and simulation that the radiation-induced leakage current increase is related to an increase in the reverse bias leakage characteristics of the gated diode which is formed by the drain epitaxial layer and the body. This mechanism does not significantly contribute to radiation-induced leakage current in typical p-channel MOS transistors. The p-channel leakage current increase is nearly identical for both biased and grounded irradiations and therefore has serious implications for long duration missions since even devices which are usually powered off could show significant degradation and potentially fail.

Effect of temperature on capacitance–voltage characteristics of SOI

The effect of temperature on capacitance–voltage ( C– V) characteristics of Si/SiO 2 interfaces in SIMOX was investigated. The results obtained for SIMOX were compared with the C– V characteristics of Si/SiO 2 and Si/SiN x devices. The results suggested that the positively charge centers in buried SiO 2 layer were located closer to the superficial Si layer of SIMOX. These positively charged centers considerably affected the capacitance of SIMOX-based devices upon increase of device temperature. It was also found that the MOS type devices fabricated using SIMOX had a higher temperature effect than MIS structures.

Temperature dependence of the electrical properties of MOS devices constructed by sol gel deposited BaTiO3 films on p-Si

The electrical properties of MOS devices with high-k insulating BaTiO3 sol gel films fabricated onto p-Si substrates, were investigated by a variety of electrical techniques. The aim was to identify the temperature dependence of the electrical properties of the MOS devices. All samples exhibit a typical MOS behaviour. The density of interface states Dit was found to decrease with decreasing temperature and lies between 1 × 1011 eV−1 cm−2 at near midgap and 3 × 1012 eV−1 cm−2 near the gap edges. The bulk-trapped charges were calculated to be between 40 and 120 nCb cm−2. The samples depicted high dielectric constants reaching values of 120. The results revealed that the sol-gel technique creates effective microelectronic devices.

To the Digital Age: Research Labs, Start-Up Companies, and the Rise of MOS Technology (review)

Reviewed by: To the Digital Age: Research Labs, Start-Up Companies, and the Rise of MOS Technology Paul E. Ceruzzi (bio) To the Digital Age: Research Labs, Start-Up Companies, and the Rise of MOS Technology. By Ross Knox Bassett. Baltimore: Johns Hopkins University Press, 2002. Pp. xii+421. $44.95. A glance at recent nonfiction best-seller lists reveals a number of popular histories of technology, which follow the conceit that some relatively obscure invention (such as the Harrison chronometer) was responsible for changing the course of world history. After reading three or four of these, one begins to wonder if this is really the right approach, even if it does sell books and therefore ought to be good for our field. There is no need here to criticize these popular works, other than to state the obvious, namely, that an invention by itself, stripped of its social and cultural components, cannot drive history. Ross Bassett does not make such an inflated claim in To the Digital Age, but in this thoroughly researched and detailed book he does reveal that much of the digitized world we inhabit today is in fact enabled by a specific type of silicon device, the Metal-Oxide-Semiconductor, or MOS, transistor. It had its drawbacks, especially slow speed, but it also carried some advantages, especially its ability to be fabricated at high densities and its parsimonious power requirements. To his credit, Bassett devotes as much attention to the social dimensions of this story as to the technical details of the invention and production of the MOS transistor itself. We learn of the transistor's champions at various laboratories, including Bell Labs, RCA, and IBM, and of how they struggled against those who favored the existing paradigm, the bipolar transistor, which switched at faster speeds. We learn of the culture of Silicon Valley and how it differed from its east coast counterparts—another topic about which much has been written, but never with the reliance on interviews and primary sources that Bassett's book features. Some of the information about Silicon Valley, such as the close relationship that Valley firms cultivated to marketing, I already knew about. Other information is new to me, especially that Stanford University was not much of an enabler of the Valley's initial success. What is most provocative about this book is that the story of the MOS transistor challenges the assumption of scholars about the nature of research and development since the Second World War. As articulated in Vannevar Bush's Science, the Endless Frontier, it gives primacy to basic research, whose practitioners need not always concern themselves with practical applications. The assumption is that the applications will come in due course, but to try to influence that trajectory is both unnecessary and counterproductive. In the story of MOS, Bassett portrays the IBM Corporation, and to a lesser extent RCA and Bell Labs, as subscribing to this belief to their own detriment, even though they accomplished significant work [End Page 892] on MOS. For it was not at IBM, RCA, or Bell Labs where MOS was perfected and pushed on to the world; rather, it was at the Intel Corporation in Mountain View, California. At Intel there was no acceptance of the old assumption about research and development; indeed, there was no separate research laboratory at all. The result was the empirical observation made by Intel cofounder Gordon Moore, and called Moore's Law after him: since about 1960, the number of transistors that one can place on a chip of silicon doubles about every eighteen months. By implication, the world of digital circuits is advancing at a rate unmatched by any other technology in history. Such a doubling simply could not have been possible with bipolar circuits, IBM's technology. It was MOS's scalability that made it so attractive to its early champions, even if few at first recognized that scalability, not switching speed, was the critical feature. Moore's Law makes historians of technology uncomfortable, especially its implication that an increase in chip density, a technical criterion, equals "progress" in general. Acceptance of this premise implies a technological determinism that people seem to accept with little...

Electrical characterization of gas sensing devices based on porous TiO2

Electrical properties of two kinds of sandwich structures (SnO 2 :F/por-TiO 2 /Ti and Si/por-TiO 2 /Pd) are investigated by the methods of I-V, C-V characteristics and DLTS in vapors of water and alcohol. It has been demonstrated that besides the change of the conductivity and of the capacitance of the por-TiO 2 layers one can also use for gas sensing the change of the high frequency capacitance of the MOS type structure, measurement of the current response at relatively low frequencies and the modification of the charge transfer between the Si bulk and states near the por-TiO 2 /Si interface.

Growth of High Quality Fluorinated Silicon Dioxide for Thin Film Transistors

AbstractThin film transistors(TFT) in microcrystalline and amorphous Si require high quality gate insulators that can be grown at low temperatures. In this paper, we show that one can oxidize Si wafers to produce high quality fluorinated silicon dioxide gate insulator using a low pressure remote plasma. The insulating film was grown on c-Si substrates using a low pressure ECR oxygen plasma, with small quantities of fluorine added to the mixture. Helium was used as the carrier gas for both oxygen and fluorine. The growth temperatures were in the range of 400–450 C. MOS type capacitors were made to judge the quality of the oxide/semiconductor interface, and interface defect densities were measured using capacitance-voltage techniques. It was found that when no fluorine was present in the oxide, the interface defect density was ∼1-2 x 1011/cm2 eV. The addition of F2 to oxygen immediately reduced the defect density by an order of magnitude, to ∼1.5 x 1010/cm2eV. The addition of more F2 slowly increased the defect density. Thermal cycling measurements showed that the semiconductor/oxide interface is very stable under cycling.

The European Photon Imaging Camera on XMM-Newton: The pn-CCD camera

The European Photon Imaging Camera (EPIC) consortium has provided the focal plane instruments for the three X-ray mirror systems on XMM-Newton. Two cameras with a reflecting grating spectrometer in the optical path are equipped with MOS type CCDs as focal plane detectors (Turner 2001), the telescope with the full photon flux operates the novel pn-CCD as an imaging X-ray spectrometer. The pn-CCD camera system was developed under the leadership of the Max-Planck-Institut fur extraterrestrische Physik (MPE), Garching. The concept of the pn-CCD is described as well as the dierent operational modes of the camera system. The electrical, mechanical and thermal design of the focal plane and camera is briefly treated. The in-orbit performance is described in terms of energy resolution, quantum eciency, time resolution, long term stability and charged particle background. Special emphasis is given to the radiation hardening of the devices and the measured and expected degradation due to radiation damage of ionizing particles in the rst 9 months of in orbit operation.

A comparison of oxidation and oxygen substitution in MoS 2 solid film lubricants

Significant advancements in the production of low friction, long wear life, sputter-deposited MoS 2 lubricant coatings have been made in the last decade. The introduction of multi-layered coatings, the establishment of careful controls on doping during DC and magnetron sputter deposition, and the implementation of ion assisted deposition have resulted in lubricants with substantially longer wear lives (up to a factor of ten greater than in the early 1980s) and lower sliding friction coefficients. A major research effort, designed to improve the performance of solid lubricants, involved a number of laboratories during this time period, resulting in these major breakthroughs. However, even with this concentrated effort, the typical investigation involved making an educated guess, based on previous experience, of the deposition conditions, target compositions, or post treatments that might be expected to provide improved performance of resulting coatings. One notable discovery during this time period was that typical MoS 2 films contain large quantities (up to 20 atom %) of oxygen substituted for sulfur in individual crystal lattices. In this paper we will compare the effects of this oxygen substitution with the effects of oxidation which involves a change in the oxidation number of the central molybdenum atoms within the crystals. A discussion of the relationship(s) between chemistry and coating structure and tribological performance will be presented with emphasis on defect chemistry and multiple phase interactions. Speculations on the role of coating chemistry in determining coating performance in applications such as in ball bearings will be presented.

Comparison of tribological characteristics of sputtered MoS 2 films coated with different apparatus

Tribological characteristics of sputtered MoS 2 films, coated with six different apparatus by five different organizations, are evaluated and compared. Ball-on-disk friction tests were carried out in vacuum, nitrogen gas and dry air environments. Some films were also evaluated in roll/slide (disk/disk edge loading) configuration with slip ratios of 0.01 and 0.1. In ball-on-disk tests in vacuum, repeatability of wear life of the same film was good, within a factor of 2.2, except for one type of film. Durability of the MoS 2 films depended largely on the type of the film, suggesting that nature of the MoS 2 film was different due to different sputtering method and/or sputtering conditions. The effect of test environment on wear life was similar for all the films, and the life was longest in nitrogen gas, followed by in dry air, and then in vacuum. Wear life in roll/slide tests was almost the same with that in ball-on-disk tests for three types of MoS 2 film. However, one type of MoS 2 film showed much longer wear life in roll/slide tests. Sputtering conditions for this film were optimized based on ball bearing tests, where the raceway surface was placed in perpendicular direction relative to an MoS 2 targets, similar with roll/slide specimens. This indicates that this film was optimized when the deposited surface was placed in perpendicular direction relative to an MoS 2 target. In roll/slide tests, higher slip ratio gave longer wear life, suggesting that sliding action had beneficial effect to develop adherent lubricating film on the surface.

Modeling of SOI-MOS capacitors C-V behavior: partially- and fully-depleted cases

A model is presented for the C-V characteristics of partially-depleted (PD) and fully-depleted (FD) SOI-MOS capacitors. The proposed model is flexible, allowing introduction of all types of nonidealities typical to MOS type structures. New formulae for the low- and high-frequency capacitances of these structures are derived. Due to the various charges stored in these structures, unusual and more complex C-V curves are obtained. C-V curves where interface-state densities have been individually introduced (one at a time) at all three SiO/sub 2/-Si interfaces of the SOI-MOS-C are also demonstrated. The model has been validated by fitting the predicted HF C-V curves for SOI-MOS-C and its inherent structure, the SIS capacitor, to the experimental data. The extracted electrophysical parameters of the studied structures, for both PD and FD cases, are very close, if not the same as the values determined during their fabrication.

Some Considerations on Tunneling Losses in Field-Effect Devices for Low-Voltage Microcontrollers

The loss power density associated with the tunneling current in a typical MOS cell with a floating gate is evaluated for high electric-field strengths in the oxide layer. Furthermore, problems related to oxide thickness are discussed.