Technology Opportunities

Low-temperature treatment achieves desired doping characteristics

Highlights

• The ability to tune the electrical properties of semiconductor nanocrystals by doping enables to improve conductance by 6 orders of magnitude.
• Standard semiconductor doping methods have proven problematic with nanocrystals since the introduction of impurity atoms into a nanocrystal that contains only a few thousands atoms causes difficulty in control and patterning.
• Novel approach for tuning the electrical conductance of semiconductor nanocrystal films by controllably inducing vacancies within the nanocrystals with thermal treatment at moderate temperatures compatible with printed electronics applications
• Enables patterning the doping profile by use of focused laser writing.

Our Innovation

An innovative approach to tuning electrical conductance of semiconductor nanocrystal films by using the controlled formation of Cu vacancies in Cu2S nanocrystals. The process is carried out at low to moderate temperatures.

Left is an electron microscope image of the nanocrystals arrays. Right graph shows film conductance vs temperature after conducting the thermal doping process at various temperatures. Repeated cooling (triangles) and heating (circle) indicate no hysteresis effect when the film is kept below ~350 K, demonstrating that the conductance increase due to the thermal doping is irreversible

Key Features

• Resulting film displays a significant, irreversible increase in conductance of up to 6 orders of magnitude.
• Allows possibility for patterned doping via optical means
• Process requires only moderate temperatures, typically under 400K.
• Process is highly reproducible.

Development Milestones

• Investigate size dependence of the thermal doping effect
• Study laser profiling method for thermal doping
• Seeking areas for application of the new technology

The Opportunity

• Ability to fabricate nanocrystal-based electronic and optoelectronic with or without laser writing to locally pattern the film’s doping profile and conductance properties
• Enables fabrication of electronic and optoelectronic devices such as transistors, solar cells and light emitting diodes in which electrical properties of deposited nanocrystal films are controllable
• The exceptional low temperatures needed for the thermal doping leading to vacancy formation in Cu2S may further benefit printed plastic electronics on flexible substrates which are incompatible with higher process temperatures.
• Production of low cost photovoltaics and photodetectors
• Nanocrystal-based field effect transistors, sensors, solar cells, light emitting diodes and additional devices