H. Wolf

Epitaxial YBa2Cu3O7−δ air‐bridge microbolometers on silicon substrates

Silicon micromachining technology is applied to fabricate free‐standing YBCO structures for low‐thermal‐mass bolometer devices. The bolometric response of the devices is studied with chopped IR illumination at a wavelength of 1.3 μm. The micromachining process leads to an enhancement of sensitivity by more than one order of magnitude. The optical responsivity of the air‐bridge bolometers measured at the midpoint of the resistive transition is 1.29 kV/W and the time constant is 81 μs. The optical noise equivalent power is 1.1×10−11 W/Hz1/2.

Metallic single electron devices fabricated using a multilayer technique

Single electron tunneling (SET) transistors were fabricated for the electrodes and for the island using two different resist masks. This technology overcomes disadvantages of the well-established shadow evaporation method usually used for the fabrication of SET devices and offers more flexibility in materials and layouts.

Charge state instabilities in the single-electron trap

We have studied the multijunction (N=9) SET trap monitored by a capacitively coupled SET-electrometer. Two dominating factors leading to the charge state instabilities at the operating temperature of T=35mK are found, namely, the background charge fluctuations and the back influence of the electrometer upon the trap.

Detection of the single electron tunneling noise using coulomb blockade electrometer

We have studied the effect of charge fluctuations in the ultrasmall metallic island, associated with quasi-random discrete electron tunneling, on a capacitively coupled Single Electron Tunneling (SET) device. Theory can explain the experiment where the SET transistor experiences the shot noise in an inner island of the multi-junction chain.

A new technology for metallic multilayer single electron tunneling devices

A new technology for the fabrication of metallic single electron tunneling (SET) transistors has been developed using different lithography steps for the preparation of the different layers. This offers the possibilty to use different materials and to avoid some disadvantages of the usual shadow evaporation method like unwanted shadows.

Silicon micromachining technique for fabricating high temperature superconducting microbolometers

Abstract Infrared detectors have been based on high temperature superconductors as bolometer resistors. To achieve low thermal mass and good thermal isolation of the bolometer device the concept of air-bridge mircrobolometers is introduced. Silicon micromachining technology is applied to prepare free-standing YBa 2 Cu 3 O 7 structures on silicon substrates. This paper describes the overall concept of air-bridge microbolometers and demonstrates the superiority of these devices compared to conventional bolometers.