High-temperature infrared radiator element and methods
An IR radiator element suitable for use as a miniature infrared emitter (micro-hotplate) in a gas sensor, IR-spectrometer or electron microscope. The micro-hotplate comprises a plate supported by multiple support arms. The plate and arms are fabricated as a MEMS device comprising a single contiguous piece of electrically-conducting refractory ceramic such as hafnium carbide (HfC) or tantalum hafnium carbide (TaHfC). Each of the arms, in addition to providing structural cantilever support for the plate ( 2 ), acts as a heating element for the plate. The plate is heated by applying a voltage across the arms. The arms may also be shaped to absorb thermomechanical stress which arises during the heating and cooling of the arms and plate. The plate, which may have an area of less than 0.05 mm2 and a thickness of between 1% and 10% of the largest dimension of the plate, for example, can be heated to 4,000 K or more and cooled again with a duty cycle of as little 0.5 ms, thereby permitting pulsed operation at frequencies of up to 2 kHz. Its small size (10-200 μm) and low power consumption (e.g. 10-100 mW) make the micro-hotplate suitable for use in cryogenic applications, in miniaturized devices or in battery-powered devices such as mobile phones.
1 . A radiator device for an IR emitter micro-hotplate, the radiator device comprising:
an IR emitter element, and a plurality of support arms, connected to the emitter element, wherein:
the emitter element is suspended by the arms, and
the emitter element is heatable to a predetermined IR emission temperature by resistive heating in the arms, wherein the emitter element is configured to be heatable to the predetermined IR emission temperature entirely or in a great majority by the said resistive heating in the arms, by thermal conduction from the arms into the emitter element, wherein the emitter element has a lower electrical resistance in comparison to the arms, so that little or no heat is generated by emitter element.
2 . The radiator device according to claim 1 , wherein the said IR emission temperature is greater than 1,600 K.
3 . The radiator device according to claim 1 , wherein the emitter element and the arms are formed as a single contiguous piece of material.
4 . The radiator device according to claim 3 , wherein the material is an electrically-conducting refractory ceramic.
5 . The radiator device according to claim 4 , wherein the ceramic comprises carbon, HfC, TaHfC or tungsten carbide.
6 . The radiator device according to claim 1 , wherein the number of arms is even, and where the even number is at least 4.
7 . The radiator device according to claim 1 , wherein the arms are elastically deformable so as to absorb thermomechanical changes in shape and/or size of the emitter element and/or of the arms during heating and cooling or the emitter element.
8 . The radiator device according to claim 1 , wherein each of the arms has a cross-section which varies along its length such that its cross-sectional area is a minimum at a region of the arm adjacent to the emitter element.
9 . An IR emitter device comprising a radiator device according to claim 1 , wherein the emitter element and the arms are encapsulated in a housing comprising an TR-transparent window.
10 . The IR emitter device according to claim 9 , wherein the housing is evacuated to 10 −3 Torr.
11 . A gas-sensing, pressure sensing, gas analyzing, IR spectrometer, SEM or TEM device comprising an IR emitter device according to claim 9 .
12 . A portable-communications device comprising a gas sensing, pressure sensing, gas analyzing, IR spectrometer, SEM or TEM device according to claim 11 .
13 . A method of generating broadband infrared radiation, comprising:
using an IR emitter device according to claim 9 , and
applying a voltage across the arms so as to heat the emitter element to a temperature greater than 1,600 K.
14 . The method according to claim 13 , comprising pulsing the voltage at a frequency greater than 200 Hz.
15 . A method of manufacturing an IR emitter device, comprising a first fabrication process of fabricating multiple radiator devices according to claim 1 on a single wafer.
16 . The method according to claim 15 , further comprising a second fabrication process of fabricating, aligned with each of the radiator devices, one or more components of an application device, in particular a gas sensing, pressure sensing, gas analyzing, IR spectrometer, SEM or TEM device, so as to produce the said application device, including the said each radiator device.
17 . A gas sensing, pressure sensing, gas analyzing, IR spectrometer, SEM or TEM device comprising an IR emitter device that includes a radiator device according to claim 1 .
18 . The radiator device according to claim 1 , wherein the arms are elastically deformable so as to absorb thermomechanical changes in shape and/or size of the emitter element and/or of the arms during heating and cooling or the emitter element.
19 . A method of generating broadband infrared radiation, comprising:
using an IR emitter device that includes a radiator device according to claim 1 , and
applying a voltage across the arms so as to heat the emitter element to a temperature greater than 1,600 K.