Using Imperfect Semiconductor Systems for Unique Identification

The secure identification of an object or electronic system is carried out through the provision of some unique internal or external characteristic. The most obvious examples of these include passwords and fingerprints that can identify a person or an electronic device, and holograms that can tag any given object to provide a check of its authenticity. Unfortunately, modern technology provides resources that enable the trust of these everyday techniques to be undermined. Identification schemes have been proposed to address these issues by extracting the identity of a system from its underlying physical structure, which is constructed such that the system is hard‐to‐ clone or predict. These systems are known as Unique Objects (UNOs) and Physically Unclonable Functions (PUFs). The aim of the work in this thesis is to create a novel type of UNO/PUF that utilises the atomic‐scale uniqueness of semiconductor devices by measuring a macroscopic quantum property of the system. The variations in these quantum properties are amplified by the existence of such atomic‐scale imperfections, meaning these devices would be the hardest possible system to clone, use the least resources and provide robust security. Such devices would be of great societal and political significance and would provide the biggest technological barrier between the good guys and the bad. Specifically, this work has introduced three distinct devices based on semiconducting systems that could provide atomic‐scale unique identification: • Electronically ‐ Fluctuations in the current‐voltage characteristics of Resonant Tunneling Diodes (RTDs) were found to provide a simple measurement of the underlying quantum state electronically. • Optically ‐ Macroscopic thin films of the two‐dimensional material, MoS2, were created by the Langmuir‐Blodgett technique for the first time and have laid the foundations for the formation of an optical analogue of an atomic‐PUF/UNO system. • Optoelectronically ‐ The Langmuir‐Blodgett technique’s flexibility was utilised to fabricate complex heterostructures that couple graphene to semiconducting nanoparticles. This system should provide an ideal system with efficient electronic and optical characteristics that would be useful in a range of applications, including unique identification.