Thermal boundary resistance in YBCO THz microbolometers at room temperature

Pierre Herman

Göteborg : Chalmers tekniska högskola, 2014. 105 s. 
http://studentarbeten.chalmers.se/publication/202172-thermal-boundary-resistance-in-ybco-thz-microbolometers-at-room-temperature

Terahertz waves are utilized for a wide range of applications, from security, medical imaging to gas spectroscopy, etc. Previous investigations in the Teraherzt and Millimeter wave group at Chalmers, has shown that antenna-integrated Y Ba2Cu3O7 (YBCO) bolometer could serve as a potential detector for this range of the electromagnetic spectrum. The detector is composed of a 70 nm thick YBCO _lm with micron sized dimension and is deposited on a crystalline Al2O3 (sapphire) substrate. Phonons, the quasi-particles associated with the lattice vibrations, transport the heat from the _lm to the substrate, but are scattered in this process. This scattering is macroscopically represented by the thermal resistance. The thermal resistance is responsible for the response and speed of these bolometers. Two parameters are varied that we believe could affect this thermal resistance. The first parameter is the thickness of the CeO2 buffer layer. This layer is situated between the YBCO layer and the sapphire substrate. Its purpose is to provide a good lattice match and chemical isolation of the YBCO layer with respect to the substrate. The range studied is 10 - 50 nm. The second parameter is the deposition temperature during the deposition of the film using pulsed laser deposition, this parameter is known to affect the YBCO film quality, however no study has investigated its influence on the thermal properties of the detector. The range studied is 780◦C − 855◦C. The thermal resistance is experimentally studied by fabricating the bolometers with above mentioned parameters and measuring them using DC (IV, Resistance-Power) and RF techniques (voltage response versus modulation frequency). Results are analyzed and compared to reported measurements as well as with the Two Temperature model. Considerable variability is present for all devices, even when fabrication parameters are kept constant. The performance was not improved by either the buffer thickness or the temperature deposition in the studied range. The effective thermal resistance ex- tracted from the DC measurements is found to be situated between 0.1.10−3cm2K/W − 1.0.10−3cm2K/W (excluding outliers). These values are not in accordance with the RF-measurements. The study suggests that additional knowledge on the phenomena involved in the heat transport is required.

Widest band amplifier ever at 235 GHz opens door to ultrafast broadband

Microphotograph of two stage-235 GHz amplifier Microwave Monolithic Integrated Circuit MMIC (Dimensions: 1.12 mm x 0.48 mm)

Read more at: http://phys.org/news/2014-03-widest-band-amplifier-ghz-door.html#jCp
http://phys.org/news/2014-03-widest-band-amplifier-ghz-door.html#jCp

(Phys.org) —An exciting collaboration between University College London, UCL, and Chalmers University of Technology has led to a world breakthrough in wide band amplifier circuit design.
An exciting research collaboration between UCL and Chalmers has resulted in the design and testing of the widest band amplifier ever reported. The work was led by Professor Herbert Zirath, Head of the Microwave Electronics Laboratory at the Department of Microtechnology and Nanoscience at Chalmers and Professor Izzat Darwazeh, Head of the Communications and Information Systems Group in UCL Electronic and Electrical Engineering.

Zirath and Darwazeh started on the joint project in the summer of 2012 aiming to design circuits suited for communication at frequencies approaching the terahertz (THz) region. A set of amplifier circuits were designed by PhD-student Klas Eriksson, manufactured by Teledyne in the USA and measured at Chalmers a few months ago.

The research team was delighted that the new amplifiers tested achieved results so close to design predictions; exceptionally wide broad band operation; from low GHz frequencies to frequencies exceeding 235 GHz and provided a gain exceeding 15dB, translating to a gain bandwidth product of approximately 1.5 THz. The design team believes this amplifier is at least twice as fast (in terms of bandwidth) as the fastest amplifier reported to-date.

"This achievement was possible both because of excellent technological advances in nanotechnology and state of the art design processes and techniques. This technology will help make ultrafast broadband possible for widespread use not only for communication systems but also for different scientific and test and measurement instrumentation," Izzat Darwazeh said.

The circuit builds on previous research and design work reported by Zirath and Darwazeh over the past two decades.

"This result is of considerable interest for the development of new products within the area of communication and instrumentation such as fast oscilloscopes, pulse amplifiers and fast fiber optic receivers," Herberth Zirath said.

 Explore further: Cooled integrated circuit amplifies with lowest noise so far

Terahertz sensor aiming for Jupiter's moons

 

   An illustration of the receiver in JUICE (Jupiter Icy Moons Explorer), which will make detailed observations of and its moons. Credit: ESA and Chalmers

 http://phys.org/news/2013-10-terahertz-sensor-aiming-jupiter-moons.html

A high performance terahertz receiver aiming for space missions such as ESA's "Jupiter icy moons explorer" has been developed in a joint European effort, led by Chalmers University of Technology

 Remote analysis of gases and vapours by heterodyne spectroscopy is a powerful tool in environmental monitoring, astronomy, and planetary research. Particularly for space applications, compact, light-weight and robust heterodyne spectrometers are necessary.
In a joint European effort, researchers have developed a heterodyne receiver which satisfies the requirements set by space missions. This is achieved by minimising the number of components in the local oscillator (LO) of the receiver, and by a high degree of integration of all of its subcomponents.
"The unique sensor is compact, light-weight, robust and operates at room temperature, a necessity for satellite missions requiring many years of operation", says project leader Jan Stake, professor at Chalmers University of Technology.
The receiver is optimised for the frequency band from 520 to 590 GHz. In this range, water vapour and a number of other important atmospheric trace gases, have significant spectral lines.
The researchers have achieved record performance in terms of sensitivity (noise).The key to this result is the high performance semiconductor devices used, and within the project a complete in-house membrane integrated Schottky diode process, suitable for terahertz applications, has been developed at Chalmers.

 

The dimensions of the receiver are approximately 17 cm x 3 cm. From left, the three circles show: 1. A SEM image of a 557-GHz Schottky mixer membrane circuit. 2. A SEM image of a 278-GHz HBV tripler circuit. 3. A photograph of a 93-GHz mHEMT MMIC x6 multiplier module. Credit: Chalmers, IAF, Wasa Millimeter Wave


"The results demonstrate that the receiver is very well suited for remote sensing of atmospheres and astronomical objects", says Jan Stake. "Due to its small mass and input power, the receiver is particularly suited for planetary missions such as ESA's JUICE (Jupiter Icy Moons Explorer) mission."
The receiver is a direct result of a project called TeraComp, a collaboration between European universities, institutes and industry, funded by the European Commission.
Within the project, Omnisys Instruments, producer of high performance electronics for space science applications, was responsible for design of mixer and the integration of the final receiver.
"Thanks to the collaboration and results generated within the TeraComp project, Omnisys has further strengthened its position in terahertz receiver technology", says Martin Kores, CEO of Omnisys. "We are now selected as a partner and supplier of the 557-GHz channel in the Industrial Consortium for SWI, which is the submillimetre wave instrument for the JUICE mission."

Chalmers graphene mixer opens up THz possibilities

http://www.zdnet.co.uk/blogs/qubits-and-pieces-10017876/swedish-teams-graphene-mixer-opens-up-thz-possibilities-10025129/
Researchers at Sweden’s Chalmers University have built a CMOS compatible graphene based electronic mixer – a device that combines multiple input signals into one or two composite outputs – that already works at microwave frequencies and could be extended to the terahertz range.

Jan Stake, professor of the research team says that the performance of the mixer can be improved by further optimising the circuit, and improving the on-off ratio. "Using a G‐FET in this new topology enables us to extend its operation to higher frequencies, thereby exploiting the exceptional properties of graphene. This paves the way for future technologies operating at extremely high frequencies."

As per this announcement on the university’s website, such a high frequency component could have applications in security radar systems, radio astronomy and environmental monitoring; all area where large arrays of highly sensitive, and compact mixers are required.

The breakthrough depends on the ability of graphene to switch between hole and electron carriers via the field effect. Because of this, the researchers built the mixer using only one transistor, making it much more compact than traditional mixers. This opens up the possibility of “advance sensor arrays for example for imaging at millimetre waves and even sub millimetre waves as G-FET technology progress” according to the announcement.

Chalmers researchers have now developed THz band measurement equipment to study the impact atmospheric gases have on climate.

MY NOTE: Earlier this month I was contacted by Wei Jan Wang who is the project manager at Chalmers
University in Göteborg, Sweden. He has promised to share some exciting material with me, about THz development which is going on there. Today, I found a draft web-post, which never made it on the blog, (probably because I simply forgot to post it), but it mentions work at Chalmers and I wanted to share it with readers.

http://asiancorrespondent.com/60388/electronics-ready-for-cutting-edge-climate-satellite-2/

PRESS RELEASE: Understanding and predicting climate change is one of the greatest challenges facing humanity this century. Chalmers researchers have now developed measurement equipment that can dramatically increase our understanding of the impact of atmospheric gases on climate.

“We have produced the space electronics of the future: something that is very small, uses very little power and offers high performance.” This is how one of the latest students at Chalmers to be awarded a PhD, Peter Sobis, describes his research within component development for space satellites.

“We can with a greater degree of accuracy now measure the composition of the atmosphere and increase our understanding of how pollutants affect our climate.”

Peter Sobis, together with Chalmers and the company Omnisys Instruments AB, has developed measurement equipment that is part of SteamR – the second largest space initiative in Sweden. The radiometer SteamR (Stratosphere Troposphere Exchange And Climate Monitor Radiometer) is the Swedish contribution to the space project PREMIER, which is being run by the European Space Agency, ESA. ESA’s task, based on continuous measurement of atmospheric gases, is to develop better climate models and create a better understanding of climate change.

This is the first time researchers have succeeded in producing an integrated and very compact sideband-separating radio receiver that offers high performance, for work in the Terahertz band. The new receiver enables simultaneous measurement of the existence of several greenhouse gases and other harmful pollutants although with a greater degree of accuracy than previously.

The atmospheric layer that SteamR will investigate is 6-28 km above the surface of the earth. Here the atmosphere is cooled down and becomes space in the layer that is most sensitive to the gas composition of the atmosphere. It will be possible to measure steam, ozone, methane, cloud and aerosols – three-dimensionally and continuously – to provide information about the composition of the atmosphere and to be able to follow the changes that are taking place.
Back in the early 1990s, Sweden (Chalmers, Rymdbolaget, Omnisys and others) were involved in satellite research with the launch of ODIN (2001), which is now celebrating 10 years in space. ODIN was built for two purposes: to search for water and oxygen deep in space and to monitor ozone and greenhouse gases in the Earth’s atmosphere.

The plan is to launch the successor, SteamR, into space within five years. A decision will be reached by the ESA next year. Omnisys is responsible for the development of the instrument’s high-frequency receiver, where several key components have been developed by Peter Sobis, Omnisys’s industrial PhD student at Chalmers.

Through Peter’s work, Omnisys and Chalmers will have a prominent position in the development of key components for environmental satellites and atmospheric research in space – from design to the production and assembly of complete systems,” states Martin Kores, President of Omnisys.

The key to this success has been ongoing collaboration between industry and the Swedish research community.

Peter Sobis’ thesis:
http://publications.lib.chalmers.se/cpl/record/index.xsql?pubid=140576

Terahertz Electronics ready for cutting edge climate satellite

Image via Wikipedia

http://asiancorrespondent.com/60388/electronics-ready-for-cutting-edge-climate-satellite-2/               PRESS RELEASE: Understanding and predicting climate change is one of the greatest challenges facing humanity this century. Chalmers researchers have now developed measurement equipment that can dramatically increase our understanding of the impact of atmospheric gases on climate.

“We have produced the space electronics of the future: something that is very small, uses very little power and offers high performance.” This is how one of the latest students at Chalmers to be awarded a PhD, Peter Sobis, describes his research within component development for space satellites.

“We can with a greater degree of accuracy now measure the composition of the atmosphere and increase our understanding of how pollutants affect our climate.”

Peter Sobis, together with Chalmers and the company Omnisys Instruments AB, has developed measurement equipment that is part of SteamR – the second largest space initiative in Sweden. The radiometer SteamR (Stratosphere Troposphere Exchange And Climate Monitor Radiometer) is the Swedish contribution to the space project PREMIER, which is being run by the European Space Agency, ESA. ESA’s task, based on continuous measurement of atmospheric gases, is to develop better climate models and create a better understanding of climate change.

This is the first time researchers have succeeded in producing an integrated and very compact sideband-separating radio receiver that offers high performance, for work in the Terahertz band. The new receiver enables simultaneous measurement of the existence of several greenhouse gases and other harmful pollutants although with a greater degree of accuracy than previously.

The atmospheric layer that SteamR will investigate is 6-28 km above the surface of the earth. Here the atmosphere is cooled down and becomes space in the layer that is most sensitive to the gas composition of the atmosphere. It will be possible to measure steam, ozone, methane, cloud and aerosols – three-dimensionally and continuously – to provide information about the composition of the atmosphere and to be able to follow the changes that are taking place.
Back in the early 1990s, Sweden (Chalmers, Rymdbolaget, Omnisys and others) were involved in satellite research with the launch of ODIN (2001), which is now celebrating 10 years in space. ODIN was built for two purposes: to search for water and oxygen deep in space and to monitor ozone and greenhouse gases in the Earth’s atmosphere.

The plan is to launch the successor, SteamR, into space within five years. A decision will be reached by the ESA next year. Omnisys is responsible for the development of the instrument’s high-frequency receiver, where several key components have been developed by Peter Sobis, Omnisys’s industrial PhD student at Chalmers.

Through Peter’s work, Omnisys and Chalmers will have a prominent position in the development of key components for environmental satellites and atmospheric research in space – from design to the production and assembly of complete systems,” states Martin Kores, President of Omnisys.

The key to this success has been ongoing collaboration between industry and the Swedish research community.

Peter Sobis’ thesis:
http://publications.lib.chalmers.se/cpl/record/index.xsql?pubid=140576