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1.
Recent improvements in the quality of diamond films grown by Chemical Vapour Deposition (CVD) have made synthetic diamond
a very attractive material for detection applications. In this paper, polycrystalline diamond films synthesised by microwave
plasma enhanced CVD using a CH4–CO2 gas mixture, previously investigated as particle detectors, have been characterised by X-ray diffraction and Raman spectroscopy.
The detector response was measured in vacuo under irradiation with 5.5 MeV α-particle from a 241Am source. A systematic study of the influence of the film structural properties on the detector performance has been carried
out by changing the methane concentration in the growth plasma and the deposition temperature. The existence of a correlation
between growth conditions, film texturing and detector performance has been demonstrated. Independently of the substrate temperature,
(1 0 0) orientated films exhibit the lowest detection efficiencies. The meas ured collection distances are smaller than the
average grain sizes and seem to be limited by trapping centres within the grains. These results are confirmed by Raman analysis.
Received: 6 January 1999 / Accepted: 18 January 1999 相似文献
2.
G. Faggio M. Marinelli G. Messina E. Milani A. Paoletti S. Santangelo G. Verona Rinati 《Microsystem Technologies》1999,6(1):23-29
A detailed structural characterisation of synthetic diamond films, previously investigated as UV photodetectors, has been
carried out by SEM, X-ray diffraction, catholuminescence (CL), micro-Raman spectroscopy and micro-photoluminescence. The films
were deposited by microwave plasma enhanced chemical vapour deposition using a CH4–CO2 gas mixture. The effect of a systematic change of the methane concentration on film morphology, preferential orientation
and crystal quality has been investigated at two different substrate temperatures, 750°C and 850°C. A strong decrease of both
band-A CL and width of the diamond Raman line at 1332 cm-1 has been observed, at lower substrate temperature, going towards (1 0 0) texturing, consistent with the attribution of band-A
luminescence to the presence of structural defects such as dislocations. A strong correlation between methane-induced texturing
and UV detector performance has been evidenced: poorly oriented films exhibit a better UV photoresponse than highly textured
films. Raman and luminescence measurements suggest that the limiting factor for the detector performance is related, rather
than to structural defects to centres of different nature, whose density strongly depends on the sample preferential orientation.
Received: 30 March 1999/Accepted: 12 April 1999 相似文献
3.
R. Bandorf H. Lüthje K. Schiffmann T. Staedler A. Wortmann 《Microsystem Technologies》2002,8(1):51-54
This paper deals with the fabrication and characterisation of friction and wear reduced nano-films for micro actuator applications.
For this investigation films of diamond-like-carbon (DLC), metal doped Me-DLC, carbon-nitride CN
x
, boron-nitride BN and alumina Al2O3 films have been applied in the thickness range of 20–500 nm. The hardness of those coatings varied between 10 and 60 GPa.
Micromechanical and microtribological properties of nano-coatings have been characterized by a modified scanning probe microscope.
Besides this a novel micro tester for abrasive wear measurement of nano coatings was used. Friction of micro-contact areas
was measured by use of a pin-on-disc tester. It turned out, that friction was – besides other parameters – dependent on determination
method and load. Friction determined at areal DLC/DLC contact zones was generally much higher (μDLC 0.1) than diamond tip versus DLC (∼μ
DLC
0.06).
Received: 19 June 2001/Accepted: 15 September 2001 相似文献
4.
This paper presents the use of micro-hotplates (MHPs) as thermal processing and in situ characterization platforms for phase transformations in thin films. MHPs are fabricated by microsystem technology processes and consist of a SiO2/Si3N4 membrane (app. 1 μm) supported by a bulk Si frame. Several embedded Pt thin films serve as heater and electrical measurement electrodes. It is shown that the MHPs have unique properties for the controlled annealing of thin film materials (up to 1270 K), as the annealing temperature and heating/cooling rates can be precisely controlled by in situ measurements. These rates can be extremely high (up to 104 K/s), due to the low thermal mass of MHPs. The high cooling rates are especially useful for the fabrication of metastable phases (e.g. Fe70Pd30) by quenching. By measuring the resistivity of a thin film under test in situ as a function of the MHP temperature, microstructural changes (e.g. phase transformations) can be detected during heating and cooling cycles. In this paper, examples are presented for the determination of phase transitions in thin films using MHPs: the solid–liquid–gas phase transition (Al), the ferromagnetic–paramagnetic phase transition (Fe–Pt) and martensitic transformations (Ni–Ti–Cu, Fe–Pd). Furthermore, it is demonstrated that crystallization processes from amorphous to crystalline (Ni–Ti–Cu) can be detected with this method. Finally the application of MHPs in thin film combinatorial materials science and high-throughput experimentation is described. 相似文献
5.
The matrix structure 200 × 200 of optoacoustic cells (OAC) for uncooled IR imager with optoelectronic reading system is fabricated
and investigated at the first time. Cells 100 μm in diameter shaped on ZnSe window and filled by xenon. Photosensitive layer
consisted of SiO2 film with adsorption range 8–14 μm. Flexible membrane 0.1 μm of thick consisted of SiO2 and Al films. Radiation temperature sensitivity and noise equivalent power with optics f/1 were 0.15 K/Hz1/2 and 10 nW/Hz1/2, respectively, and the thermal response time was below 30 ms.
The article is published in the original. 相似文献
6.
D. ZilliAuthor VitaeP.R. BonelliAuthor Vitae A.L. CukiermanAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(1):169-176
Multi-walled carbon nanotubes (MWCNTs) are successfully processed in the form of thin films (buckypapers), and their morphology and electrical behaviour are characterized. The MWCNTs are synthesized by the floating catalyst chemical vapour deposition process. The effects of a sequence of treatments applied for MWCNTs purification on the buckypapers electrical behaviour are also examined. Nanocomposite thin films constituted of pristine and purified MWCNTs and Pd nanoparticles are prepared in order to evaluate their viability as H2 sensors at room temperature. For this purpose, the electrical resistance of the nanocomposite films in atmospheres with different H2 concentrations, is determined. Scanning electron microscopy (SEM) images show that the buckypapers and the nanocomposite films are 2D structures constituted by randomly oriented MWCNTs. The buckypapers present a semiconductor-like electrical behaviour as determined by the standard four point method. Room temperature resistivity values of around 10−3 Ω m are assessed. Nanocomposite films show different electrical behaviour depending on the purification treatment applied to the MWCNTs employed. Furthermore, the electrical resistance of the nanocomposite films is found to increase when the measurements are performed in H2 atmosphere. Values of H2 sensitivity at room temperature of the nanocomposite films up to 2.15% are determined for H2 average concentration higher than 350 ppm with short recovery time. 相似文献
7.
J. P. Carmo M. F. Silva J. F. Ribeiro R. F. Wolffenbuttel P. Alpuim J. G. Rocha L. M. Gon?alves J. H. Correia 《Microsystem Technologies》2011,17(8):1283-1291
This paper presents an approach for generating a well-defined cooling pattern over an area of tissue. An array of solid-state
microcoolers is used, which could be included in a probe that provides local cooling. This medical instrument can be used
for removal of scar tissue in the eye or for the rapid stopping of bleeding due to micro-cuts, which makes it a useful tool
to medical doctors and could make surgery more secure to the patient. The array of microcoolers is composed of 64 independent
thermo-electric elements, each controlled using an integrated circuit designed in CMOS. The independent control allows the
flexible programming of the surface temperature profile. This type of control is very suitable in case abrupt temperature
steps should be avoided. Cooling by lateral heat flow was selected in order to minimize the influence of heat by dissipation
from the electronic circuits. Moreover, a thermo-electric component with lateral heat allows fabrication of the cooling elements
using planar thin-film technology, lithography and wet etching on top of the silicon wafer. This approach is potentially CMOS
compatible, which would allow for the fabrication of the thermo-electric elements on top of a pre-fabricated CMOS wafer as
a post-process step. Each pixel is composed of thin-films of n-type bismuth telluride, Bi2Te3 and p-type antimony telluride, Sb2Te3, which are electrically interconnected as thermocouple. These materials have excellent thermoelectric characteristics, such
as thermoelectric figures-of-merit, ZT, at room temperatures of 0.84 and 0.5, respectively, which is equivalent to power-factors, PF, of 3.62 × 10−3 W K−1 m−2 and 2.81 × 10−3 W K−1 m−2, respectively. The theoretical study presented here demonstrates a cooling capability of 15°C at room temperature (300 K ≈ 27°C).
This cooling performance is sufficient to maintain a local tissue temperature at 25°C, which makes it suitable for the intended
application. A first prototype was successfully fabricated to demonstrate the concept. 相似文献
8.
9.
In order to achieve monolithic integration of thermoelectric power sensor and its amplification system and improve the measurement
accuracy of microwave power, a voltage source model is researched in this paper. And the thermoelectric power sensor is designed
and fabricated using MEMS technology and GaAs MMIC process. It is measured in the X-band (8–12 GHz) with the input power in
100 mW range. When the input microwave power is at 10, 50 and 100 mW, respectively, the frequency dependent coefficient k1 is −0.073, −0.39 and −0.82 mV/GHz, respectively. The sensitivity coefficient k2 is 0.311, 0.303, 0.293, 0.284 and 0.279 mV/mW at 8, 9, 10, 11 and 12 GHz, respectively, and has an excellent linearity. Based
on the voltage source model, the feedback coefficient of its amplification system is set to 0.0078 × Pin to compensate the loss power caused by frequency dependent characteristic. In addition to miniaturization and low cost, an
advantage using this model is significantly improved measurement accuracy. 相似文献
10.
Ming TanAuthor VitaeYao WangAuthor Vitae Yuan DengAuthor Vitae Zhiwei ZhangBingwei Luo Junyou Yang Yibin Xu 《Sensors and actuators. A, Physical》2011,171(2):252-259
Oriented thermoelectric (TE) p-Sb2Te3 and n-Bi2Te3 thin films with special nanostructures have been synthesized by a simple vacuum thermal evaporation technique. The composition and microstructure of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), presenting a well preferential crystal growth with dense slender columnar grains grown perpendicular to the substrate, and energy dispersive X-ray spectrum (EDX) indicating the compositions distribution in the films. The electric transport properties, i.e., conductivity and Seebeck coefficient, and the thermal transportation of the oriented films show optimized properties. Prototype devices were built up by p and n elements in series and parallel circuits. The largest output power and cooling could be achieved in Sb2Te3 parallel device with Pmax = 6.51 μW at ΔT = 106 K, and cooling of 4.1 K at 2 V. The 24-pair p-n couples series device could output maximum voltage of 313 mV at ΔT = 102 K. The power generation and the cooling of the devices show times enhanced TE performances than those consisting of common films. The results proved that introducing nanostructures into films is an effective choice to obtain high-efficient micro TE device. 相似文献
11.
This paper reports the effect of pulse current with different frequencies on the morphology and mechanical properties of nickel
(Ni) films deposited by electroplating. The pulse frequency varies from 0 (DC) to 500 Hz while the duty cycle (T
on/T
off) is 1 during electroplating. The average roughness and deposition rate of Ni films decrease with the increasing frequency.
The smoothest Ni surface with average roughness of 16.5 nm is achieved at the frequency of 500 Hz while the deposition rate
reaches a nearly stable rate of 0.04 μm/min. The surface concentration of ions does not vary with time at a sufficiently high
frequency with a long off time for ion to diffuse onto the surface. It will result in much more nuclei formed on the surface
of cathode at a limited growth rate to get small grains for smooth morphology. The nanohardness of Ni film initially decreases
rapidly from 3.9 to 1.18 GPa at 0 to 10 Hz, respectively, then increases to about 4.87 GPa in the range of 100–200 Hz, and
decreases slowly to 4.0 GPa at 500 Hz. The stiffness of Ni films electroplated by pulse current at 100–200 Hz is higher than
that by dc electroplating. The compromised Ni film with smooth morphology, good hardness and proper deposition rate is obtained
at frequency of 100–200 Hz under the current density of 3 Adm−2. 相似文献
12.
A combined experimental and computational study of the Ca5Si3 phase is presented. Its’ electronic structure and lattice stability are investigated by first principles methods: four different crystal lattices have been investigated by means of density functional theory (DFT) calculations and pseudopotentials within the generalized-gradient approximation using the VASP code. The Ca5Si3 phase is predicted to undergo an high pressure transition: the lattice transition tI32(Cr5B3-type) → tI32(W5Si3-type) has been predicted by DFT to occur at 14.9 GPa. The electronic and band structure of the tI32 Cr5B3-type lattice is calculated and discussed. The Ca5Si3 phase ground state structure is predicted to be a metal with a peaked density of states below the Fermi energy and a sharp minimum right above it. Experimentally the low temperature resistivity and heat capacity of the Ca5Si3 phase have been measured between 2 and 300 K and discussed in view of our computational predictions and available literature. The Ca5Si3 tI32(Cr5B3-type) standard pressure polymorph exhibits a metallic temperature dependence of the electric conductivity in agreement with the DFT predictions. 相似文献
13.
This work explores the microstructure and magnetic properties of electrodeposited Co-Zn thin films. Using pulse-reverse electroplating
technique, Co-rich Co-Zn films are deposited 0.4–1.9 μm thick from aqueous sulfate-based baths at low temperature (55°C).
The influence of current density (25–100 mA/cm2) and electrolyte Zn concentration (0–0.28 M) on the microstructure and magnetic properties are investigated. All of the Co-Zn
films exhibit higher out-of-plane coercivity, as compared to in-plane. With increasing current density, the out-of-plane coercivity
decreases from 50 to 40 kA/m (628–500 Oe). The influence of the Zn concentration in the electrolyte is more pronounced, affecting
the grain size, film composition, and magnetic properties. The best magnetic properties were obtained from a bath with 0.21 M
Zn and an average current density of 25 mA/cm2, resulting in a Co97Zn3 composition and an out-of-plane coercivity of 92 kA/m (1,160 Oe). 相似文献
14.
A. ForleoAuthor Vitae L. FranciosoAuthor VitaeS. CaponeAuthor Vitae F. CasinoAuthor VitaeP. SicilianoAuthor Vitae O.K. TanAuthor VitaeH. HuiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,154(2):283-287
SnO2 nanorods were successfully deposited on 3″ Si/SiO2 wafers by inductively coupled plasma-enhanced chemical vapour deposition (PECVD) and a wafer-level patterning of nanorods layer for miniaturized solid state gas sensor fabrication were performed. Uniform needle-shaped SnO2 nanorods in situ grown were obtained under catalyst- and high temperature treatment-free growth condition. These nanorods have an average diameter between 5 and 15 nm and a length of 160-300 nm. The SnO2-nanorods based gas sensors were tested towards NH3 and CH3OH and gas sensing tests show remarkable response, showing promising and repeatable results compared with the SnO2 thin films gas sensors. 相似文献
15.
Pulsed laser deposited (PLD) Y-doped BaZrO3 thin films (BaZr1-xYxO3-y/2, x = 0.2, y > 0), were investigated as to their viability for reliable humidity microsensors with long-term stability at high operating temperatures (T > 500 °C) as required for in situ point of source emissions control as used in power plant combustion processes. Defect chemistry based models and initial experimental results in recent humidity sensor literature [1] and [2]. indicate that bulk Y-doped BaZrO3 could be suitable for use in highly selective, high temperature compatible humidity sensors. In order to accomplish faster response and leverage low cost batch microfabrication technologies we have developed thin film deposition processes, characterized layer properties, fabricated and tested high temperature humidity micro sensors using these thin films. Previously published results on sputtering Y-doped BaZrO3 thin films have confirmed the principle validity of our approach [3]. However, the difficulty in controlling the stoichiometry of the films and their electrical properties as well as mud flat cracking of the films occurring either at films thicker than 400 nm or at annealing temperature above 800 °C have rendered sputtering a difficult process for the fabrication of reproducible and reliable thin film high temperature humidity microsensors, leading to the evaluation of PLD as alternative deposition method for these films.X-ray Photoelectron Spectroscopy (XPS) data was collected from as deposited samples at the sample surface as well as after 4 min of Ar+ etching. PLD samples were close to the desired stoichiometry. X-ray diffraction (XRD) spectra from all as deposited BaZrO3:Y films show that the material is polycrystalline when deposited at substrate temperatures of 800 °C. AFM results revealed that PLD samples have a particle size between 32 nm and 72 nm and root mean square (RMS) roughness between 0.2 nm and 1.2 nm. The film conductivity increases as a function of temperature (from 200 °C to 650 °C) and upon exposure to a humid atmosphere, supporting our hypothesis of a proton conduction based conduction and sensing mechanism. Humidity measurements are presented for 200–500 nm thick films from 500 °C to 650 °C at vapor pressures of between 0.05 and 0.5 atm, with 0.03–2% error in repeatability and 1.2–15.7% error in hysteresis during cycling for over 2 h. Sensitivities of up to 7.5 atm−1 for 200 nm thick PLD samples at 0.058 atm partial pressure of water were measured. 相似文献
16.
A solid immersion holographic method for the recording of refractive-index and surface-relief modulated gratings with a period of 0.2–1 μm in amorphous films of chalcogenide semiconductors As2S3 and As–S–Se has been developed and studied. The angular selectivity of holographic recording in amorphous chalcogenide thin films can be improved significantly by a decrease of grating period. The possibility to use the amorphous chalcogenide films as a media for holographic recording and storage of information with high density is discussed. 相似文献
17.
Nam Gyu ChoAuthor Vitae In-Sung HwangAuthor VitaeHo-Gi KimAuthor Vitae Jong-Heun LeeAuthor VitaeIl-Doo KimAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):366-371
This work presents a simple and versatile route to produce macroporous p-type metal oxide thin films. Two-dimensional arrays of p-type NiO films with a hollow hemisphere structure were fabricated by colloidal templating and RF-sputtering followed by a subsequent heat treatment. The diameter and shell thickness of the NiO hemisphere were 800 nm and 20 nm, respectively. X-ray diffraction and high-resolution transmission electron microscopy analysis indicate that the pure NiO phase with grain size of 10 nm was obtained at calcination temperatures that exceeded 450 °C. Close-packed arrays of hollow NiO hemispheres were found to exhibit p-type gas sensing properties against (CO, H2, C3H8, CH4, NO2, and C2H5OH), leading to significantly enhanced responses to C2H5OH (Rgas/Rair = 5.0 at 200 ppm). 相似文献
18.
Micromachined active sliders based on head load/unload on demand systems is an interesting concept technology for ultra-high
magnetic recording density of more than 100 Gb/in2. The active sliders that we proposed use PZT thin films as a microactuator and control the slider flying height of less than
10 nm. It is necessary to develop high performance microactuators in order to achieve active sliders operating at very low
applied voltage. This paper describes the development of novel PZT thin films for active sliders. The sol–gel fabrication
process for PZT thin films is developed and the fundamental characteristics for the PZT thin films are investigated. It is
confirmed that the PZT thin films have good ferroelectric properties. Furthermore, novel thin film microactuators are proposed.
The feature is that the sol–gel PZT thin films (thickness 540 nm) are deposited on the sputtered PZT thin films (thickness
300 nm) fabricated on bottom Pt/Ti electrodes. Therefore, the novel thin films consist of a thermal SiO2 layer and the sputtered and sol–gel PZT thin films layers sandwiched with upper Pt and bottom Pt/Ti electrodes on a Si slider
material. Fabricating the diaphragm microactuator, the piezoelectric properties for the novel composite PZT thin films are
studied. As a result, the piezoelectric strain constant d
31 for the novel PZT thin films is identified to be 130 × 10−12 m/V. This value is higher than conventional monolithic PZT thin films and it is found that the novel composite PZT thin films
have the good piezoelectric properties. This suggests the feasibility of realizing active sliders operating at lower voltage
under about 10 V.
Received: 22 June 2001/Accepted: 17 October 2001 相似文献
19.
In this work first commercially available SiC-transistor prototypes were tested with regard to their applicability in high
temperature electronic circuits for sensor signal conditioning.
The influence of the temperature on the device behaviour (drain-saturation current, gate leakage current, I–V-characteristics, long-term effects) was investigated. The devices showed reliable operation up to 450 °C. The maximum forward
transconductance g
m
and the short circuit drain source current I
DSS
decreased to approximately 30% of the room temperature values. Also, a slight increase of the pinch-off voltage V
p
was observed. The gate leakage current I
GSS
rose with temperature, staying below 1 μA at 450 °C. A pre-ageing study was carried out to verify changes in the device characteristics
with time. The devices were exposed to a 270 °C environment and it was observed that the DC parameters tend to stabilise after
about 100 h.
From the I–V-characteristics the SPICE parameters were extracted for a series of temperatures, allowing the design and optimisation of
amplifier gain stages. The SPICE device simulation results are in good agreement with the measured characteristics.
Received: 28 November 1996/Accepted: 2 December 1996 相似文献
20.
This paper is concerned with an array of neutral-type neural networks with hybrid nonlinear coupling, which is composed of
discrete-delay coupling and distributed-delay coupling. The discrete-delay considered in this system is assumed to vary over
an interval (0 < h
1 ≤ τ
1(t) ≤ h
2), where the lower and the upper bounds are known. Based on Lyapunov–Krasovskii (L–K) functional and Kronecker product technique,
by introducing several new free-weighting matrices, two novel criterions are acquired to ensure the global synchronization
of the proposed networks, which are proved to be much less conservative than some exiting results. Moreover, the derivative
of discrete-delay can take any value. Finally, numerical examples are provided to show the effectiveness of the proposed results. 相似文献