Thermal design issues and performance of microcalorimeter arrays at sub-Kelvin temperatures

We have produced 5/spl times/5 pixel arrays of microcalorimeters using bulk micromachining. Analysis of our data provides the thermal conductivity parameters of Si/sub x/N/sub y/ 1 /spl mu/m thick membranes at 100 mK. Moreover we find that the thermal transport at 100 mK in Si beams, with dimensions 1.25 mm /spl times/ 0.35mm /spl times/ 35/spl mu/m (length /spl times/ height /spl times/ width) is dominated by ballistic phonons with a mean free path of 110 /spl mu/m. These thermal parameters can be used for modelling future 32 /spl times/ 32 pixel arrays. In addition we operated three pixels in a 5 /spl times/ 5 array of microcalorimeters and find that the pixel to pixel reproducibility is very good. When used as an X-ray microcalorimeter individual pixels have a thermal decay time of 200 /spl mu/s is and their energy resolution is between 6 and 7 eV for 5.89 keV X-ray photons

Radiative ballistic phonon transport in silicon-nitride membranes at low temperatures

We studied the phonon transport in free-standing 1 µm thick silicon-nitride membranes at temperatures around 100 mK. By varying the geometry of the membranes and the dimensions of the heater element, we are able to distinguish between radiative and diffuse phonon transport. The data indicate that the transport is radiative ballistic with a lower limit to a phonon mean-free path of about 1 mm and that the probability for specular reflection from the surface is at least 0.99. The tested silicon-nitride membranes were grown on Si(100), Si(110), and polycrystalline-Si and the transport properties show no dependency on the substrat

Principles of the Field Theory of High Temperature Superconductivity in Underdoped Copper-Oxides

Here I extend my last work about the origin of the pseudo-gaps in underdoped cuprates (arXiv: cond-mat. 1011.3206), to include the mechanism of superconductivity. This is done by adapting the formalism of the double correlations in systems with nested Fermi surfaces to the semi one dimensional system of strings of holes. It is proposed that magnetic interaction is crucial for the establishment of the pseudogap and the high temperature superconductivity. It is shown that superconductivity disturbs the completeness of the strings of holes, and creates fluctuations in their shapes. This, in turn, reduces the magnetic interaction and the pseudogap order.Comment: This paper has been withdrawn by the author. 27 page

Conduction electrons at surfaces and interfaces

Contains fulltext : mmubn000001_143808370.pdf (publisher's version ) (Open Access)Promotores : H. van Kempen en P. van Bentum105 p

Performance of hot-electron bolometers for infrared photometry and X-ray micro-calorimetry

The performance of voltage biased superconducting transition edge bolometers for infrared photometry and X-ray micro-calorimetry is described. Experimental results for the resistance–temperature curve of the superconducting phase thermometer, the current–voltage characteristic of the bolometer, and its current noise are presented and evaluated. Excess current noise turns out to be present when the bolometers are biased in the superconducting transition. The possible origin of this excess noise is shortly discussed. For the infrared bolometer an NEP of 2 at 270 mK is obtained. The X-ray micro-calorimeter resolution is 60 eVFWHM at 155 mK for 5.9 keV X-rays, a factor 2.6 above the thermodynamical limit

Fabrication and characterization of infrared and sub-mm spiderweb bolometers with low Tc superconducting transition edge thermometers

Spiderweb bolometers with a superconducting transition edge thermometer combine a high sensitivity and absorption efficiency for far infrared and sub-mm radiation with a low susceptibility to high energetic particles. They are among the most promising detectors today for future astronomy applications. In this paper we present our fabrication process for a fully integrated bolometer consisting of absorber, thermometer and suspension structure, based on micromachining of a silicon nitride membrane and various thin film deposition and etching steps. The optimization of Ti/Au transition edge thermometers is described, as well as electrical measurements on a fully integrated bolometer, indicating an electrical noise equivalent power of 2×10 -17 W/vHz at an operating temperature of 270 mK

Trade-off study of the SQUID read-out for a hot-electron micro-calorimeter

SQUIDs and their read-out electronics for application with a hot-electron bolometer are considered in detail. This results in a theoretical trade-off study between a Hypres two-stage DC-SQUID, APF, DROS and an Oxford Instruments' Internal Relaxation Oscillation Mode SQUID. The study shows that only a Hypres DC-SQUID can meet the requirements on noise, dynamic range and speed as derived from the application for an X-ray micro-calorimeter. The scope for redesign of the other types of SQUID is addressed

Fabrication and characterization of infrared and sub-mm spiderweb bolometers with low Tc superconducting transition edge thermometers

Spiderweb bolometers with a superconducting transition edge thermometer combine a high sensitivity and absorption efficiency for far infrared and sub-mm radiation with a low susceptibility to high energetic particles. They are among the most promising detectors today for future astronomy applications. In this paper we present our fabrication process for a fully integrated bolometer consisting of absorber, thermometer and suspension structure, based on micromachining of a silicon nitride membrane and various thin film deposition and etching steps. The optimization of Ti/Au transition edge thermometers is described, as well as electrical measurements on a fully integrated bolometer, indicating an electrical noise equivalent power of 2×10 -17 W/vHz at an operating temperature of 270 mK

Kinetic inductance detectors based receiver array architectures for imaging at THz frequency

A novel strategy for broad band focal plane array design, resulting from the two years long cooperation between TNO and SRON (Space Research Organization Netherlands), is proposed. Its purpose is to couple the radiation from a Large F/D reflector system to an array of Kinetic Inductance detectors that are being investigated at SRON to be used in Space science missions such as SPICA