The development of organic optoelectronics has progressed rapidly. These devices are now an essential part of our lives (e.g. mobile phone, computer, energy applications and touch-enabled applications). With increasing demand for mass production of low-cost materials, researchers are readily seeking new innovative materials to replace conventional materials based on polymers or small molecules. Metal oxides are one of the most interesting classes of materials, but their current processing is incompatible with organic systems and their application in this field requires new simplified methods of deposition.
In this thesis, zinc acetate dihydrate (ZnAc2H2O) has been selected as a precursor for the formation of ZnO. It is inexpensive, has high volatility and demonstrates the oligomerisation of basic zinc acetate (BZA) in vacuum, which is known as a molecular model of ZnO. While there are limited reports of BZA films and powder in the literature, this is the first time that it is fully characterised. The BZA film is prepared on room temperature substrates, with and without pre-coating of 3,4,9,10-perylenetetracharboxylic dianhydride (PTCDA) using organic molecular beam deposition (OMBD), which convey high quality films with well-controlled film thickness and high purity. Contrasting the morphology of the two films, the growth mode for the former is known as “Frank-van-der-Merwe” whereas the latter is “Stranski-Krastanov”. This formation is critical since film orientation and morphology can dramatically alter device performance.
A new method for processing metal oxide using small molecules at room temperature has been developed. This method depends on exposing small molecule film to vacuum ultraviolet (VUV) light, generating a photon energy of 7.2 eV (172 nm) via several degradation mechanisms. The effect of atmosphere and irradiation length are evaluated by altering the partial pressure of oxygen and adjusting the height of the sample stage during the VUV process, respectively. The presence of oxygen molecules inducing oxygen radicals and ozone plays a major role in the degradation reaction. This is significantly greater than the effect of irradiance.
Finally, a new, room temperature method, VUV process, is used on two BZA films to explore whether this is suitable to the formation of ZnO. Both films exposed to VUV light under different atmospheric conditions show the formation of M-O-M species, with optimised results for high vacuum conditions. Varying the irradiation length results in further enhancement of M-O-M. Furthermore, the underlying PTCDA is preserved during UV exposure. This suggests that ZnO formation acts as an effective barrier layer protecting the underlying organic components.