Hybrid organic-inorganic, self-assembling system

Highlights

• When a superconductor is placed in contact with a normal metal, the critical temperature of the superconductor, TC, is usually suppressed and signs of weak superconductivity are induced in the normal material. This is called a proximity effect.
• Related proximity effects have also been observed for non-metallic systems such as Anderson insulators and molecules.
• Less common is the inverse proximity effect, where critical temperature of the superconductor is increased when attached to a non-superconducting material.

Our Innovation

Increasing critical temperature of a niobium (Nb) film by attaching gold nanoparticles to its surface by organic linkers. Self-assembled monolayer of gold nano-particles are attached through organic linker molecules to the Nb film. The observed effect strongly depends on the nanoparticles' size, the length of the organic linkers, and the thickness of the Nb film (see diagram below).

Schematic drawings of self-assembled monolayers of three types of organic molecules adsorbed on top of Nb films

(a) (I) 3-methylpropane bis-trichlorosilane (di-silane) which forms a 3-nm-thick layer, (II) mercapto propyl silane (MPS), which forms a 0.5-nm-thick monolayer, and (III) tricloro (octadecyl) silane (OTS) which forms a 3 nm thick layer. The Au nano-particles were chemically linked only to the first two types of molecules.

(b) The differential resistance as a function of the normalized temperature measured at zero magnetic field. The temperature is normalized to TC of the corresponding bare evaporated Nb film (Black). The blue and red curves show results obtained for samples with 5 and 10 nm Au NPs, respectively, linked to the Nb film via di-silane molecules. 

In green, data for 5 nm NPs linked by the MPS organic monolayer. The inset shows a high-resolution SEM image of the Au NPs adsorbed on top of the Nb film.

(c) 50nm sputtered Nb film coated with 10-nm NPs linked by the di-silane and MPS organic layer showing about 10% increase in TC. Very small changes in the critical temperature are observed when using non-linking OTS molecules. Note that the relative improvement of the 50 nm film is larger than that of the 150 nm film.

Key Features

• Applications for the production of high temperature superconductors
• May be used to developed planar lithography and new routes for superconducting-normal junction devices.
• Nanoparticles can be selectively adsorbed on top of the devices, creating local critical temperature changes. This effect could be used for patterning areas with high and low critical temperature on the superconducting film.

Development Milestones

• Seeking funding for ongoing research

The Opportunity

• High temperature superconductors (HTS) can superconduct at temperatures above the boiling point of liquid nitrogen, which makes them cheaper to cool than low temperature superconductors.

Can be used for:

• Low thermal loss current leads for low temperature superconductor devices
• RF and microwave filters
• In specialist scientific magnets, particularly where size and electricity consumption are critical (while HTS wire is much more expensive than LTS in these applications, this can be offset by the relative cost and convenience of cooling)
• Magnetic sensors.
• Single photon detectors