The development of ZnO nanoparticles in poly(styrene-acrylic acid), [PS]m/[PAA]n, diblock copolymer on large area Si wafers is reviewed and the study of ZnO nanoparticle properties in PS-PAA copolymer system with different parameters, m/n of 159/63 and 106/17, is reported. These diblock copolymers are expected to exhibit spherical nanosized domains of the acrylic acid blocks due to microphase separation in solid phase but with domain size and density dependent on their respective molecular block lengths. Self-assembly of ZnO nanoparticles within these domains enabled control of nanoparticle size and density. The self-assembly process involved the doping of copolymer with ZnCl2 precursor followed by delivery of nanocomposite films onto wafers by a spincasting process and subsequent conversion of ZnCl2 to ZnO. The chemical analysis of these nanocomposite films and nanoparticles were performed using X-ray Photoelectron spectroscopy (XPS) which verified the conversion to ZnO. Imaging of the nanocomposite films with atomic force microscopy (AFM) showed that particles in [PS]159/[PAA]63 and [PS]106/[PAA]17 have a size distribution of 250-350 nm and 10-60 nm, respectively. Effect of precursor overdoping on size distribution of the nanoparticles is also discussed.
The formation of self-assembled ZnO nanoclusters using diblock copolymers for self-assembly is reviewed and the development of the ZnO nanoclusters within two different copolymer systems -- poly styrene-acrylic acid and poly styrene methacrylic acid, with block repeat unit ratios of 159/63 and 318/78, respectively, are reported. Different copolymer systems were used to observe the size dependence of the nanoclusters on the molecular block lengths of the copolymers. The synthesis scheme of the nanoclusters relied on the thermodynamically driven microphase separation of the diblock copolymers in solid phase due to immiscibility of the covalently bonded polymers in the copolymer. The scheme involved the formation of ZnCl2 nanoclusters on Si and SiO2 surfaces by doping of the copolymer systems with ZnCl2 in liquid phase at room temperature and application of the doped solution onto the surfaces by spin-on casting, followed by conversion to ZnO nanoclusters using a new dry technique of ozone exposure. The dry method effectively converted ZnCl2, without any loss of ZnO during conversion and with better conversion rate than the wet chemical method developed previously. XPS verified the conversion to ZnO and AFM showed the spherical morphology of the nanoclusters. Technique was developed using RIE for obtaining stand-alone nanoclusters on both surfaces.