Composite nanoparticle and photodetector comprising the nanoparticle

An apparatus comprising

• at least one composite particle and a layer of two dimensional material wherein the at least one composite particle is coupled to the layer of two dimensional material to enable absorption of light by the composite particle to be detected by the layer of two dimensional material;
• wherein the composite particle comprising:
• an inner core comprising a dielectric material;
• a first coating layer provided overlaying at least part of the inner core;
• a second coating layer provided overlaying the first coating layer where the second coating layer comprises a semi-conductor material;
• and
• wherein the first coating layer comprises a plasmonic material configured to enable surface plasmons to be generated at a boundary between the inner core and the first coating layer and a boundary between the first coating layer and the second coating layer.

A method comprising:

• forming an inner core comprising a dielectric material;
• forming a first coating layer overlaying at least part of the inner core;
• forming a second coating layer overlaying the first coating layer where the second coating layer comprises a semi-conductor material and is selected to generate excitons in response to incident light, wherein the selected thickness of the second coating layer inhibits a recombination of excitons with the semiconductor material;
• and
• wherein the first coating layer comprises a plasmonic material configured to enable surface plasmons to be generated at a boundary between the inner core and the first coating layer and a boundary between the first coating layer and the second coating layer and wherein the inner core, first coating layer and second coating layer form a composite particle.