Fabrication of Zinc Oxide and Nanostructured Porous Silicon Composite Micropatterns on Silicon

Abstract

The luminescent properties of zinc oxide (ZnO) and nanostructured porous silicon (PSi) make these materials very appealing for photoemission applications. The current study reports on the fabrication of a composite of ZnO and nanostructured porous silicon micropatterns (ZnO + PSi micropatterns) onto heavily-doped silicon surfaces. The proposed composite micropattern is devoted to the future development of light-emitting diodes. The fabrication of the ZnO + PSi micropatterns was carried out in a two–step process. (1) A regular hexagonal micropattern of a photoresist/ZnO stack was fabricated by UV lithography on crystalline silicon substrates. (2) Before being lifted off the photoresist, nanostructured PSi micropatterns were fabricated by electrochemically etching the exposed areas of the silicon substrate. Subsequently, wet etching of the photoresist was carried out for the final development of the composite ZnO and PSi micropatterns. Further, thin films of ZnO and nanostructured PSi layers were characterized. In particular, their photoluminescent properties were analyzed, as well as their morphology and composition. The experimental PL results show that the ZnO layers have emission broadbands centered at (2.63 eV, blue), while the PSi layers show a band centered at (1.71 eV, red). Further, the emission peaks from the PSi layers can be tuned by changing their fabrication conditions. It was observed that the properties of the ZnO thin films are not influenced by either the surface morphology of PSi or by its PL emissions. Therefore, the PL properties of the composite ZnO + PSi micropatterns are equivalent to those featuring the addition of PSi layers and ZnO thin films. Accordingly, broadband optical emissions are expected to arise from a combination between the ZnO layer (blue band) and PSi (red band). Furthermore, the electrical losses associated with the PSi areas can be greatly reduced since ZnO is in contact with the Si surface. As a result, the proposed composite micropatterns might be attractive for many solid-state lighting applications, such as light-emitting diodes.

Special Issue “1D, 2D, and 3D ZnO: Synthesis, Characterization, and Applications”

“…Additionally, they enhance the PL emissions by combining blue emissions from the ZnO areas with red emissions from the PSi nanostructures. The authors show that the composite ZnO+PSi micropatterns could be of interest for photoemission applications and hence desirable for many solid-state lighting applications, such as light-emitting diodes [14].…”

Tunable and white light photoluminescence from ZnO on porous Si with the addition of carbon quantum dots

“…For these reasons, the combination of the two materials has sparked significant interest in terms of creating tunable photoluminescent materials. The most common approach is the creation of a composite material through the deposition of ZnO on a porous Si substrate and a subsequent annealing process [18][19][20][21][22][23][24][25][26][27][28][29]. This approach follows the single emissive layer route for white light creation.…”

“…For example, composite porous Si/ZnO materials have been shown to emit on wavelengths between 380 and 680 nm [24] or from 550 to 850 nm [30]. Very little effort has been made to combine the two materials in a device structure that independently utilizes their properties [28].…”

Porous silicon pillar structures/photosynthetic reaction centre protein hybrid for bioelectronic applications

“…Silicon has been applied in biosensors since the very beginning of the development of biosensing technologies [13][14][15]. After the discovery of PSi and recognising its unique optical properties [16,17], new prospects were revealed in the area of sensing [18] and biosensing [19][20][21]. In the simplest case, the light interference effect of the PSi photonic structure provides a characteristic reflectance spectrum with a specific reflection mode, which is sensitive to any surface modification [8,22].…”