Graphene (0002)/Diamond (111) Heterojunction with High Piezoresistive Response

ABSTRACT Diamond and graphene are emerging as promising successors to silicon‐based materials for semiconductor applications, particularly when integrated into graphene/diamond heterostructures. However, fabricating high‐quality graphene (0002) atomic layers on diamond (111) with intimate contact—mostly desired for device integration—remains a great challenge. Here, we report a strategy to realize a covalently bonded, graphene (0002)/diamond (111) heterojunction using thermal electron irradiation. Combining structural characterization with theoretical calculations, the formation mechanism and energy band characteristics of this junction structure were clarified, and the microscopic mechanism of hexagonal diamond (lonsdaleite) acting as an intermediate state before its transformation into graphene layers was proposed. The heterostructure exhibits a high piezoresistive response under the present testing configuration, with a gauge factor of −1149. This performance is attributed to two key factors: first, the heterojunction‐induced formation of an electron‐rich layer on the diamond surface; and second, a significant stress‐induced increase in the density of states of carbon C 2p orbitals within the diamond layer. Leveraging diamond's intrinsic properties, piezoresistive chips based on this structure may offer opportunities for high‐temperature, radiation‐tolerant, wide‐range, and fast‐response sensing applications after further device‐level optimization and validation. These results provide a useful basis for developing diamond‐based semiconductor and sensing devices.