Ian Sorensen

Adhesion, surface morphology, and gas sensing characteristics of thin‐gold‐film chemical sensors

Thin films of the Au, Au/Cr, Au/Ni/Cr, and Au/Pd/Cr systems were deposited on alumina substrates at ambient temperature and 250 °C in a high‐vacuum resistance heated evaporator, and annealed at 300, 450, and 600 °C for 1 h in air, respectively. The gold films with a Cr adhesive layer exhibited improved adhesion of the films to the substrate. Pull‐off tests demonstrated that the adhesion of the Au/Cr films deposited at ambient temperature more than doubled after annealing at 600 °C. The surface morphology of the gold films was observed using scanning electron microscopy. The sheet resistance of each layer was also investigated using a four‐point probe method. Finally, the sensing characteristics as exemplified by observed resistance changes during exposure of the films to a gas were measured at room temperature for hydrogen sulfide (H2S). The sensitivity of the Au/Cr system for H2S is the highest of the four systems. As a result of the Auger‐electron spectroscopy analysis, the Au/Ni/Cr and Au/Pd/Cr systems...

Thermally induced changes in the resistance, microstructure, and adhesion of thin gold films on Si/SiO2 substrates

The resistance as a function of annealing temperature for thin gold films on a SiO2 layer on silicon (100) passes through a minimum near 600 °C for times at temperature ≤60 min. The structural changes associated with this electrical behavior have been investigated by scanning tunneling microscopy and scanning electron microscopy. Annealing temperatures as low as 100 °C affect the microstructure as well as reducing the resistance. Recrystallization and grain growth occur with increasing temperature, and the high surface energy of gold relative to SiO2 results in nucleation and growth of porosity above about 600 °C which contributes to an abrupt increase in resistance. The adhesion of gold to SiO2 was improved at elevated temperatures (≥600 °C).