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The optical properties of ZnO nanorods realized by an advanced low-temperature aqueous chemical growth on both silicon and plastic substrates are presented. Systematic photoluminescence investigations in the temperature range of 4–293K reveal strong and well-resolved near-band-edge emission even for rods on plastic substrate, and a weak deep-level emission. At intermediate temperatures phonon replicas of excitonic lines are observable. The optimum molar concentration range of the solution for obtaining nanorods of good optical quality is shown to lie between 0.025M and 0.075M. The large linewidth of the near-band-edge emission (∼10meV), its temperature dependence, and the absence of sharp excitonic transitions indicate that this emission is a result of transitions from a band of donor states.

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Aqueous chemical growth (ACG) is a low-temperature approach that is only weakly influenced by the substrate and allows for the growth of ZnO nanopillars on various substrates. ACG is an efficient way to generate wafer-scale and densely packed arrays of ZnO nanopillars even on polymer materials. Photoluminescence (PL) characterisation clearly shows a comparatively strong band-edge luminescence even at room temperature that is accompanied with a rather weak visible luminescence in the yellow / orange spectral range. We introduce a rather simple postgrowth lithographic technique. Patterning of ZnO nanopillars even on layered conducting and flexible substrate materials using ACG as a low-temperature growth technique is demonstrated. The economical potential for future applications and devices using ZnO nanopillar arrays is discussed.1 Introduction ZnO materials have received broad attention in the last years due to its wide direct bandgap of 3.37 eV at room temperature, large exciton binding energy (60 meV in bulk ZnO), piezoelectric properties, excellent chemical and thermal stability and pronounced ability to build a variety of nanostructures. Nanosized materials are of special interest due to novel electrical, mechanical, chemical and optical properties that are introduced by surface and quantum confinement effects [1]. Gas-phase approaches that are based on evaporation and condensation steps are frequently used due to their simplicity and high-quality products [2][3][4][5]. However, the economic potential of gas-phase grown structures is restricted because these approaches require rather expensive and / or insulating substrate materials [6]. In recent years aqueous chemical growth (ACG) approaches gain in importance because ACG is a costefficient and low temperature growth technique. Vayssieres et al. developed an ACG process under hydrothermal like conditions [7,8]. A further growth approach is based on a two step process: first generation of a nucleation layer followed by an aqueous chemical growth step [6,9,10]. Up to now only little progress was achieved with respect to generation and position control of well defined geometric arrays of ZnO nanostructures. Recently the report of Hsu et al. shows directed bottom up growth of ZnO nanorods on prestructured Si (001) wafers using a combination of expensive electron beam and microcontact printing techniques [11]. Here we report on further developments and characterisation of the two step ACG technology. Moreover we introduce a rather simple lithographic patterning technique that allows for the generation of well defined geometric arrays on various substrate materials.