Synthesis and Characterization of Cr1−xWxN Thin Films for Thermoelectric Applications

Sammanfattning

Thermoelectric materials allow for interconversion between heat and electricity, making them promising for energy harvesting applications such as waste heat recovery. Current commercial materials are limiting large scale implementation due to scarcity and high cost, thus motivating the search for other options. Realizing thin films of thermoelectric materials permits their use in microdevices thus extending their use. Furthermore, this also allows for new and creative ways in which the thermoelectric properties can be tuned. CrN has been considered for thermoelectric applications as it: (i) has promising thermoelectric properties and (ii) consists of abundant elements, making it a more sustainable option than current materials. The thermoelectric properties, however, need to be improved upon before CrN can be fully implemented in real applications. In the present thesis, the goal is to achieve dilute doping of W in CrN thin films by means of improving the thermoelectric properties motivated by previous studies. Both CrN and Cr1−xWxN f ilms are grown on c-plane sapphire substrates by DC reactive magnetron sputtering with varying process parameters. The films are characterized structurally by XRD, morphologically by SEM and thermoelectric measurements are made to evaluate the effect of dilute W doping on the thermoelectric properties. Dilute doping of 2.5 at.% W at metal sites in CrN was achieved and thermoelectric measurements indicate that the properties were enhanced where the thermoelectric power factor increased from 1.5 × 10−4 to 3.1 × 10−4 W/mK2.