Surface properties of an InGaZnO4 layer with a monolayer formed using a phosphonic acid: wettability, work function, and thermal stability

The surface properties of an InGaZnO4 (IGZO) layer with a monolayer formed on the surface using octadecyl phosphonic acid (ODPA) or (1H, 1H, 2H, 2H-heptadecafluorodecyl) phosphonic acid (FDPA) were investigated. Surface roughness, wettability, and work function were investigated using atomic force microscopy, water contact angle measurement, and photoelectron yield spectroscopy, respectively. The reaction time of monolayer formation on an IGZO layer was discussed based on the measured contact angle. An ODPA-monolayer formed at a slightly higher rate than an FDPA-monolayer. The work function measurement provided an estimate of the density of the molecule in the monolayer. Furthermore, the measured contact angle was used to evaluate the thermal stability of a monolayer. The evaluation suggested that annealing above 500 K causes monolayer desorption for both ODPA- and FDPA-monolayers.