| 1. |
- Ackelid, Ulf, et al.
(författare)
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Ethanol sensitivity of palladium-gate metal-oxide-semiconductor structures
- 1986
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 7:6, s. 353-355
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen-sensitive palladium-gate MOS structures heated above 150°C show sensitivity to ethanol vapor. The effect is probably due to catalytic dehydrogenation of adsorbed ethanol molecules on the surface of the palladium gate.
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| 2. |
- Fare, T., et al.
(författare)
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Quasi-static and high frequency C(V)-response of thin platinum metal—oxide—silicon structures to ammonia
- 1988
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Ingår i: Sensors and Actuators. - : Elsevier. - 0250-6874. ; 14:4, s. 369-386
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Tidskriftsartikel (refereegranskat)abstract
- Quasi-static and high frequency (1 MHz) capacitance—voltage characteristics are reported for thin Pt (⩽6 nm) MOS capacitors for exposures to ammonia in a background atmosphere of 20% O2/Ar. The ammonia-induced voltage shift of the quasi-static capacitance—voltage characteristics is always greater than or equal to the shift of the high-frequency characteristics for a given ammonia concentration. We discuss the differences in the ammonia response for the case of the two different contact metals, Al or Pd. The quasi-static results can be used to show that the decreased sensitivity with Pt film thickness may be only partly related to the high impedance of the Pt film itself. Based on these results, we argue that the intrinsic ammonia sensitivity of Pt films (less than about 20 nm thick) decreases with decreasing film thickness. We also report some results for hydrogen exposure of 1.5 nm Pt films and discuss them together with complementary measurements of the film impedance. It is concluded that ammonia interacts quite differently with the thin Pt film compared to hydrogen. The findings in this paper support a recently proposed model for the ammonia sensitivity of thin catalytic metal films.
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| 3. |
- Fare, T., et al.
(författare)
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Reversible interaction of hydrogen with thin layers of thermally grown silicon dioxide
- 1988
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 63:11, s. 5507-5513
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Tidskriftsartikel (refereegranskat)abstract
- Some effects of hydrogen on the electrical properties of Pd‐metal‐thin (≊10 nm) oxide‐silicon capacitors are reported. High‐frequency (1 MHz) and quasistatic capacitance voltage curves are measured at 100 °C as a function of hydrogen partial pressure in a background atmosphere of 20% O2/Ar. Besides the standard hydrogen‐induced shift of the capacitance‐voltage characteristics we find: (1) an increase in the accumulation capacitance with increasing hydrogen partial pressure, and (2) a nonmonotonic increase in the quasistatic capacitance minimum with increasing hydrogen pressure. The relative increase in the accumulation capacitance is shown to be related to the square of the hydrogen‐induced voltage shift (and hence to the square of the concentration of hydrogen atoms at the Pd‐SiO2 interface). We discuss our findings, based on existing hydrogen‐silicon dioxide models, to interpret the effects of hydrogen on the high‐frequency and quasistatic capacitance characteristics.
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| 4. |
- Lundström, Ingemar, et al.
(författare)
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Gas sensors based on catalytic metal-gate field-effect devices
- 1986
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Ingår i: Sensors and Actuators. - : Elsevier. - 0250-6874. ; 10:3-4, s. 399-421
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Forskningsöversikt (refereegranskat)abstract
- The properties of gas-sensitive semiconductor devices with catalytic metal gates are reviewed, with emphasis on field-effect structures sensitive to hydrogen-containing molecules like H2, NH3, H2S, alcohols, ethylene etc.A brief review of some of the developed device structures are given. The principles of hydrogen sensors with Pd gates are described in some detail. Ammonia-sensitive field-effect devices with thin catalytic metal gates are discussed. Applications of gas-sensitive field-effect devices for studies of catalytic reactions together with electron spectroscopy in UHV systems, for medical diagnosis, in leak detectors and as biosensors are reviewed.
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| 5. |
- Spetz, Anita, et al.
(författare)
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HYDROGEN AND AMMONIA RESPONSE OF METAL-SILICON DIOXIDE-SILICON STRUCTURES WITH THIN PLATINUM GATES
- 1988
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 64:3, s. 1274-1283
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen and ammonia sensitivity of metal‐oxide‐semiconductor (MOS) structures with platinum gates between 3 and 70 nm thick was investigated. The response to these gases was measured as a shift in the capacitance‐voltage (C‐V) curve of the MOS structure along the voltage axis. The measurements were made at an elevated temperature, mainly at 150 °C, where chemical reactions take place on the surface of the catalytic metal. The main purpose of the investigation was to determine if hydrogen and ammonia are detected by similar mechanisms. It is concluded that hydrogen molecules are dissociated and hydrogen atoms give rise to a dipole layer at the metal‐oxide interface, similar to the behavior of hydrogen in hydrogen sensitive MOS structures with thick catalytic metal, normally Pd, gates. Ammonia, on the other hand, appears to be detected through surface potential changes of the Pt film, which are capacitively coupled to the semiconductor surface through voids in the thin metal film.
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| 6. |
- Spetz, Anita, et al.
(författare)
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Optimization of ammonia-sensitive metal-oxide-semiconductor structures with platinum gates
- 1987
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Ingår i: Sensors and Actuators. - : Elsevier. - 0250-6874. ; 11:4, s. 349-365
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia gas-sensitive MOS capacitors with platinum as a thin active metal gate have been studied. The influence of parameters such as the thickness and area of the platinum film on the ammonia sensitivity was investigated. Thicknesses of about 10 to 30 nm of platinum were found to be favourable for a large response to small ammonia concentrations. It was further observed that with aluminium as a thick contact material, the response to ammonia was independent of the area of the platinum film. Theoretical and experimental C(V curves were compared to elucidate the mechanism behnd the ammonia sensitivity. it is concluded that the sensitivity arises from the thin catalytic Pt film.
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| 7. |
- Spetz, Anita, et al.
(författare)
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Structure and ammonia sensitivity of thin platinum or iridium gates in metal-oxide-silicon capacitors
- 1989
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 177:1-2, s. 77-93
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Tidskriftsartikel (refereegranskat)abstract
- Metal-oxide-semiconductor (MOS) structures with thin discontinuous platinum or iridium gates have a strong sensitivity to ammonia gas. Surface potential changes caused by NH3-derived species adsorbed on the metal grains are assumed to be capacitively coupled to the semiconductor surface through the cracks in the metal film. This causes a negative shift along the voltage axis of the capacitance-voltage curve of the MOS capacitor. The structure of the platinum or iridium film is thus of crucial importance for the response to NH3. Transmission electron microscopy (TEM) studies were therefore performed with specially prepared substrates which enabled thin metal films on silicon dioxide to be studied by TEM without any further treatment of the films. TEM micrographs of platinum films showed that the metal coverage and crack density corresponded well to the NH3 sensitivity of the films. Iridium films with a reproducible film structure were made through evaporation of about 10 nm of iridium at a pressure below 2 × 10-7 Torr at room temperature. Iridium films prepared in that way exhibited a very good NH3 response. Heat treatments of platinum and iridium films were shown to influence the structure of the metal film. H2 and NH3 treatments (in synthetic air) initiated structural changes at lower temperatures. For platinum films a change in film structure was always coupled with a decrease in the speed of response to NH3. For metal films with very large grains the surface potential change due to NH3 did not couple under the whole metal grain, which provides strong support for the proposed model of NH3 sensitivity.
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| 8. |
- Winquist, Fredrik, et al.
(författare)
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Biosensors based on ammonia sensitive metal-oxide-semiconductor structures
- 1985
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Ingår i: Sensors and Actuators. - : Elsevier. - 0250-6874. ; 8:2, s. 91-100
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Tidskriftsartikel (refereegranskat)abstract
- The physical principles behind the ammonia gas sensitivity of thin catalytic metal-oxide-semiconductor structures are briefly described. in particular, it is shown that room temperature operation is possible with good performance. Biosensors based on the combination of these structures with immobilized enzymes are also described. Several substrates of clinical interest, such as urea, creatinine and amino acids are determined by the combination of the structure and corresponding immobilized enzymes. A flow injection analysis system and a 'bioprobe' are described and discussed.
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