scholarly journals Thermoelectric Photosensor Based on Ultrathin Single-Crystalline Si Films †

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1427 ◽  
Author(s):  
Gustavo Gonçalves Dalkiranis ◽  
Pablo Ferrando-Villalba ◽  
Aitor Lopeandia-Fernández ◽  
Llibertat Abad-Muñoz ◽  
Javier Rodríguez-Viejo
Keyword(s):  
Phonon Scattering ◽  
Ambient Pressure ◽  
High Vacuum ◽  
Laser Diodes ◽  
Argon Laser ◽  
High Sensitivity ◽  
Open Circuit ◽  
Thermal Mass ◽  
Slight Reduction ◽  
Si Films

Ultrathin Si films have a reduced thermal conductivity in comparison to Si bulk due to phonon scattering at the surfaces. Furthermore, the small thickness guarantees a reduced thermal mass (in the µJ/K range), which opens up the possibility of developing thermal sensors with a high sensitivity. Based on these premises, a thermoelectric (TE) microsensor based on ultrathin suspended Si films was developed and used as a thermal photosensor. The photoresponse of the device was evaluated with an argon laser (λ = 457 nm) with a variable power ranging from 0 to 10 mW in air at atmospheric pressure, with laser diodes at 406 nm, 520 nm and 638 nm wavelengths, and fixed powers in high vacuum conditions. The responsivity per unit area, response time (τ) and detectivity (D*) of the device were determined in air at ambient pressure, being 2.6 × 107 V/Wm2, ~4.3 ms and 2.86 × 10 7   c m H z ( 1 / 2 ) W − 1 , respectively. Temperature differences up to 30 K between the central hot region and the Si frame were achieved during open-circuit voltage measurements, with and without laser diodes. During illumination, the photogeneration of carriers caused a slight reduction of the Seebeck coefficient, which did not significantly change the sensitivity of the device. Moreover, the measurements performed with light beam chopped at different frequencies evidenced the quick response of the device. The temperature gradients applied to the thermoelectric Si legs were corrected using finite element modeling (FEM) due to the non-flat temperature profile generated during the experiments.

scholarly journals Thermoelectric Microsensor Based on Ultrathin Si Films

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 1517
Author(s):  
Gustavo Gonçalves Dalkiranis ◽  
Pablo Ferrando-Villalba ◽  
Aitor Lopeandía-Fernández ◽  
Llibertat Abad-Muñoz ◽  
Javier Rodriguez-Viejo
Keyword(s):  
Seebeck Coefficient ◽  
Diode Laser ◽  
Atmospheric Pressure ◽  
Open Circuit Voltage ◽  
High Vacuum ◽  
Argon Laser ◽  
Open Circuit ◽  
Thermal Mass ◽  
Light Illumination ◽  
Si Films

We show the use as a thermal photosensor of a thermoelectric (TE) microsensor based on ultrathin suspended Si films. The reduced thickness of the structural films enhances the extremely large thermal insulation of the sensing area (~43 µW/K), since phonons scatter in the surfaces, and guarantees a reduced thermal mass (in the µJ/K range). The sensitivity of the device is evaluated by heating with an argon laser (λ = 457 nm) in the range 0–10 mW, reaching sensitivities of around 6 × 108 V/(W·m2) in high vacuum conditions and 5 × 107 V/(W·m2) in environments of air at atmospheric pressure. Open circuit voltage measurements with and without light illumination with a 406 nm diode laser operating at 4 mW were conducted at temperature differences up to 50 K between the central hot region and the Si frame. The slight decrease of the Seebeck coefficient is related to the increase of carriers by photogeneration.

Microreactors for Thin-Film Calorimetry

2002 ◽  
Vol 741 ◽  
Author(s):  
J. Rodríguez-Viejo ◽  
M. Chacón ◽  
A.F. Lopeandía ◽  
M.T. Clavaguera-Mora ◽  
Leonel R. Arana ◽  
...  
Keyword(s):  
Heat Capacity ◽  
High Vacuum ◽  
Transient State ◽  
High Sensitivity ◽  
Symmetric Design ◽  
Input Power ◽  
Cdse Nanocrystals ◽  
Thermal Mass ◽  
Heating Rates ◽  
Calorimetric Measurements

ABSTRACTWe have designed and developed a calorimeter that is capable of measuring the heat released by ultrathin films in the temperature range from 77 to 1050 K. Semiconductor processing techniques are used to fabricate the microreactors. The symmetric design of the Pt heaters in the microreactor channel provide a good temperature profile across the active region of the membrane making it suitable for accurate calorimetric measurements. The low thermal mass of our system allows for a high sensitivity. The effective heat capacity of the microcalorimeters with a 200 nm SixNy membrane is 0.14 μJ/K at room temperature. In high vacuum heating rates of 2×106 K/s have been achieved. Under these conditions the microcalorimeter works as an adiabatic scanning calorimeter and therefore heat capacity is directly obtained from the input power. A thermal characterization of the microcalorimeters in the transient state and calorimetric measurements on indium thin films and films made of CdSe nanocrystals are briefly discussed to show the potentiality of the microreactors.

Recent Developments In Monochromatic Microprobe X-Ray Fluorescence (MMXRF)

1998 ◽  
Vol 4 (S2) ◽  
pp. 378-379
Author(s):  
Z. W. Chen ◽  
D. B. Wittry
Keyword(s):  
Materials Science ◽  
High Vacuum ◽  
Three Dimensional ◽  
High Sensitivity ◽  
X Rays ◽  
Fluorescence Excitation ◽  
X Ray ◽  
Quantitative Microanalysis ◽  
Recent Developments ◽  
Fifth Order

A monochromatic x-ray microprobe based on a laboratory source has recently been developed in our laboratory and used for fluorescence excitation. This technique provides high sensitivity (ppm to ppb), nondestructive, quantitative microanalysis with minimum sample preparation and does not require a high vacuum specimen chamber. It is expected that this technique (MMXRF) will have important applications in materials science, geological sciences and biological science.Three-dimensional focusing of x-rays can be obtained by using diffraction from doubly curved crystals. In our MMXRF setup, a small x-ray source was produced by the bombardment of a selected target with a focused electron beam and a toroidal mica diffractor with Johann pointfocusing geometry was used to focus characteristic x-rays from the source. In the previous work ∼ 108 photons/s were obtained in a Cu Kα probe of 75 μm × 43 μm in the specimen plane using the fifth order reflection of the (002) planes of mica.

scholarly journals A Self-Powered Nanogenerator for the Electrical Protection of Integrated Circuits from Trace Amounts of Liquid

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhuang Hui ◽  
Ming Xiao ◽  
Daozhi Shen ◽  
Jiayun Feng ◽  
Peng Peng ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
High Performance ◽  
Printed Circuit Board ◽  
Short Circuit ◽  
High Sensitivity ◽  
Short Circuit Current ◽  
Fast Response ◽  
Open Circuit ◽  
Circuit Board ◽  
Self Powered

Abstract With the increase in the use of electronic devices in many different environments, a need has arisen for an easily implemented method for the rapid, sensitive detection of liquids in the vicinity of electronic components. In this work, a high-performance power generator that combines carbon nanoparticles and TiO2 nanowires has been fabricated by sequential electrophoretic deposition (EPD). The open-circuit voltage and short-circuit current of a single generator are found to exceed 0.7 V and 100 μA when 6 μL of water was applied. The generator is also found to have a stable and reproducible response to other liquids. An output voltage of 0.3 V was obtained after 244, 876, 931, and 184 μs, on exposure of the generator to 6 μL of water, ethanol, acetone, and methanol, respectively. The fast response time and high sensitivity to liquids show that the device has great potential for the detection of small quantities of liquid. In addition, the simple easily implemented sequential EPD method ensures the high mechanical strength of the device. This compact, reliable device provides a new method for the sensitive, rapid detection of extraneous liquids before they can impact the performance of electronic circuits, particularly those on printed circuit board.

scholarly journals Why Pressure Scales Cause So Much Confusion

1993 ◽  
Vol 1 (8) ◽  
pp. 5-6
Author(s):  
Anthony D. Buonaquisti
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Ambient Pressure ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Scanning Auger Microprobe ◽  
The Mean ◽  
Scanning Electron

Pressure scales can be extremely confusing to new operators. This is not surprising. To my mind, there are three primary areas of confusion.Firstly, the pressure of gas inside an instrument changes over many orders of magnitude during pumpdown. The change is about 9 orders of magnitude for a traditional Scanning Electron Microscope and about 13 orders of magnitude for an ultra-high vacuum instrument such as a Scanning Auger Microprobe.To give an idea about the scale of change involved in vacuum, consider that the change in going from ambient pressure to that inside a typical ultra high vacuum system is like comparing one meter with the mean radius of the planet Pluto's orbit. The fact is that we don't often get to play with things on that scale. As a consequence, many of us have to keep reminding ourselves that 1 X 10-3 is one thousand times the value of 1 X 10-6 - not twice the value.

An Ultrafast Thin-Film Microcalorimeter with Monola Yer Sensitivity (J/m2)

1995 ◽  
Vol 398 ◽  
Author(s):  
S.L. Lai ◽  
P. Infante ◽  
G. Ramanath ◽  
L.H. Allen
Keyword(s):  
Thin Film ◽  
Heating Rate ◽  
Current Pulse ◽  
High Sensitivity ◽  
Melting Process ◽  
Thermal Mass ◽  
Calorimetric Measurements ◽  
Calorimetric Technique ◽  
Dc Current ◽  
Thin Film Membrane

ABSTRACTWe introduce a high-sensitivity (∼1 J/m2) scanning microcalorimeter that can be used to perform direct calorimetric measurements on thin film samples at ultrafast heating rate (∼104 °C/s). This novel microcalorimeter is fabricated by utilizing SiN thin-film membrane technology, resulting in dramatically reduced thermal mass of the system. Calorimetric measurements are accomplished by applying a dc-current pulse to the thin-film metal (Ni) heater which also serves as a thermometer, and monitoring the real-time voltage and current of the heater. The temperature of the system and the energy delivered to the system are then determined. This calorimetric technique has been demonstrated by measuring the melting process of thin Sn films with thickness ranging from 13 to 1000 Å, and shows potential for calorimetric probing of irreversible reactions at interfaces and surfaces, as well as transformations in nanostructured materials.

Chalcogenide Glass Thin Films for Nanodipole Junctionless Photovoltaics

2011 ◽  
Vol 1322 ◽  
Author(s):  
Sakina Junaghadwala ◽  
Daniel G. Georgiev ◽  
Victor G. Karpov ◽  
Rossen Todorov ◽  
Nanke Jiang
Keyword(s):  
Thin Films ◽  
Chalcogenide Glass ◽  
Open Circuit Voltage ◽  
High Vacuum ◽  
Practical Interest ◽  
Open Circuit ◽  
Photovoltaic Devices ◽  
Scanning Calorimetry ◽  
New Type ◽  
Initial Results

ABSTRACTWe examine the potential of Bi-Ge-Se chalcogenide glass films as materials for a new type of photovoltaic devices, referred to as junctionless nanodipole PV. Glasses of a chemical composition providing a significant optical absorption were synthesized in quartz ampoules from high-purity Bi, Ge, and Se elements by a conventional melt quenching technique. This material was then used to deposit thin films with different thicknesses on various substrates by thermal evaporation under high-vacuum conditions. The original bulk glasses and the films were characterized by electron microscopy with EDS, XRD, Raman spectroscopy, differential scanning calorimetry, and spectrophotometry. Open-circuit voltage (Voc) readings under incandescent illumination were obtained from the as-deposited and annealed films. Results from this characterization work are presented and discussed. Although the efficiency of nanodipole PV material structures, based on this material remains of no practical interest, our initial results indicate a possible path for the implementation of the nanodipole PV concept.

Prevention of Corner Voiding in Selective CVD Deposition of Titanium Silicide on SOI Device

1999 ◽  
Vol 564 ◽  
Author(s):  
Jer-shen Maa ◽  
Bruce Ulrich ◽  
Lisa Stecker ◽  
Greg Stecker ◽  
Sheng Teng Hsu
Keyword(s):  
Flow Rate ◽  
Void Formation ◽  
Drain Current ◽  
Deposition Process ◽  
Open Circuit ◽  
Titanium Silicide ◽  
Deposition Condition ◽  
Soi Devices ◽  
Si Films

AbstractIn the application of selective CVD of titanium silicide to SOI devices, voids were observed at the bottom corner of the spacers, which caused reduction of drain current and in extreme cases formed an open circuit. Test structures were constructed to monitor void formation. It was found the voiding became serious when the thickness of the Si film was reduced. Adjusting the deposition condition by reducing the TiCi4 flow rate or by using a two-step deposition process was able to significantly reduce the chance of void formation. On very thin Si films, voiding can be prevented by depositing a selective Si layer prior to silicide deposition.

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