Towards flexible asymmetric MSM structures using Si microwires through contact printing

This paper presents development of flexible metal-semiconductor-metal devices using silicon (Si) microwires. Monocrystalline Si in the shape of microwires are used which are developed through standard photolithography and etching. These microwires are assembled on secondary flexible substrates through a dry transfer printing by using a polydimethylsiloxane stamp. The conductive patterns on Si microwires are printed using a colloidal silver nanoparticles based solution and an organic conductor i.e. poly (3,4-ethylene dioxthiophene) doped with poly (styrene sulfonate). A custom developed spray coating technique is used for conductive patterns on Si microwires. A comparative study of the current–voltage (I–V) responses is carried out in flat and bent orientations as well as the response to the light illumination of the wires is explored. Current variations as high as 17.1 μA are recorded going from flat to bend conditions, while the highest I on/I off ratio i.e. 43.8 is achieved with light illuminations. The abrupt changes in the current response due to light-on/off conditions validates these devices for fast flexible photodetector switches. These devices are also evaluated based on transfer procedure i.e. flip-over and stamp-assisted transfer printing for manipulating Si microwires and their subsequent post-processing. These new developments were made to study the most feasible approach for transfer printing of Si microwires and to harvest their capabilities such as photodetection and several other applications in the shape of metal-semiconductor-metal structures.