Thermoelectric- and hot-electron effects in graphene devices

Sammanfattning: A technology of encapsulation of graphene in Parylene was introducedas an alternative to encapsulating graphene in hBN. Edge contacts to theencapsulated graphene in this case showed resistivity down to 14 Ohm um,which is the lowest reported value so far. The resulting graphene devicesshowed a high carrier mobility (up to 30000 cm2/(V s) at 300K), low doping(down to 10^11 cm2) and were stable in time. Possibility of encapsulatingalso CVD graphene for large-scale device fabrication was shown.This Parylene encapsulation technology was used for fabrication of thermoelectricgraphene devices and radiation detectors. Since the Seebeck coef-cient in graphene is high, the thermoelectric eects are strong. A dual-gateddesign was used to create an intrinsic graphene thermocouple. Due to a weakcoupling between phonons and electrons in graphene, the electrons can havesignicantly higher temperature than the phonons. These devices allowedfor simple measurement of electron temperature in graphene. When coupledto an antenna, such a device served as a radiation detector. Even underunoptimized conditions the detectors showed responsivity up to 700 V/Wand noise level down to 18 pW/Hz^0.5. The response time was estimated tobe less than 1.2 ps.