Preparation, structural and electrical properties of zinc oxide grown on silicon nanoporous pillar array

Polycrystalline thick film of zinc oxide （ZnO） is grown on a unique silicon substrate with a hierarchical structure, silicon nanoporous pillar array （Si-NPA）, by using a vapour phase transport method. It is found that as-grown ZnO film is composed of closely packed ZnO crystallites with an average size of -10 μm. The film resistivity of ZnO/SiNPA is measured to be -8.9Ωcm by the standard four probe method. The lengthwise Ⅰ-Ⅴ curve of ZnO/Si-NPA heterostructure is measured. Theoretical analysis shows that the carrier transport across ZnO/Si-NPA heterojunction is dominated by two mechanisms, i.e. a thermionic process at high voltages and a quantum tunnelling process at low voltages.

Temperature-Dependent Photoluminescence from GaN/Si Nanoporous Pillar Array

A GaN/Si nanoheterostructure is prepared by growing wurtzite GaN on a silicon nanoporous pillar array （Si-NPA） with a chemical vapor deposition method. The temperature evolution of the photoluminescence （PL） of GaN/Si- NPA is measured and the PL mechanism is analyzed. It is found that the PL spectrum is basically composed of two narrow ultraviolet peaks and a broad blue peak, corresponding to the near band-edge emission of GaN and its phonon replicas, and the emission from Si-NPA. No GaN defect-related PL is observed in the as-prepared GaN/Si-NPA. Our experiments prove that Si-NPA might be an ideal substrate for preparing high-quality Si-based GaN nanomaterials or nanodeviees.

Time-Resolved Photoluminescence Study of Silicon Nanoporous Pillar Array

A silicon nanoporous pillar array （Si-NPA） is thought to be a promising functional substrate for constructing a variety of Si-based optoelectronic nanodevices, due to its unique hierarchical structure and enhanced physical properties. This makes the in-depth understanding of the photoluminescence （PL） of Si-NPA crucial for both scientific research and practical applications. In this work, the PL properties of Si-NPA are studied by measuring both the steady-state and time-resolved PL spectrum. Based on the experimental data, the three PL bands of Si-NPA, i.e., the ultraviolet band, the purple-blue plateau and the red band are assigned to the oxygen-excess defects in Si oxide or silanol groups at the surface of Si nanocrystallites （nc-Si）, oxygen deficiency defects in Si oxide, and band-to-band transition of nc-Si under the frame of quantum confinement combining with the surface states like Si=O and Si-O^i bonds at the surface of nc-Si, respectively. These results may provide some novel insight into the PL process of Si-NPA and may be helpful for clarifying the PL mechanism.

Enhancing electrolyte ion diffusion via direct ink writing pillar array structure of graphene electrodes for high-performance microsupercapacitors

The graphene-based microsupercapacitors(MSCs)suffer from graphene aggregation issue in electrodes.It reduces the electrolyte ions transportation in the electrodes to degrade the charge storage ability of MSCs,hampering their practical application.Increasing the electrolyte ions transportation in the electrodes can boost the charge storage ability of MSCs.Herein,we design and experimentally realize pillar array structure of graphene electrodes for MSCs by direct ink writing technology.The graphene electrodes with pillar array structure increase the contact area with electrolyte and short the electrolyte ions transport path,facilitating electrolyte ions transport in electrodes.The MSCs exhibit high areal capacitance of 25.67 mF·cm^(−2),high areal energy density of 20.54μWh·cm^(−2),and high power density of 1.45 mW·cm^(−2).One single MSCs can power timer for 10 min and pressure sensor more than 160 min,showing high practical application possibility.This work provides a new avenue for developing high performance MSCs.