Porous silicon filled with Pd/WO₃–ZnO composite thin film for enhanced H₂ gas-sensing performance

Abstract

Here, pure ZnO, WO 3 and Pd/WO 3 -ZnO composite porous thin films were successfully synthesized directly on porous silicon by a reactive DC magnetron sputtering technique. A sensor based on the Pd/WO 3 -ZnO composite porous thin films showed remarkably improved H 2 sensing performance with good stability and excellent selectivity compared to that of pure WO 3 and ZnO, at a relatively lower operating temperature (200 C) and with a low detection range of 10-1000 ppm. The enhanced response can be attributed to the heterojunction formed between two dissimilar materials. The underlying mechanism behind their good performance for H 2 gas was discussed in detail.

Nanosilicon-Based Composites for (Bio)sensing Applications: Current Status, Advantages, and Perspectives

“…), which play a crucial role for the effective detection of (bio)molecules. Mainly, MOx nanolayers/nanoparticles can be deposited over a nano-Si surface through the following techniques: (i) RF and DC magnetron sputtering [24,34,36,37,120,121,123,124,125,126]; (ii) sol–gel/hydrothermal synthesis + spin coating [17,26,127,128,129,130,131]; (iii) drop casting technique + pulsed laser ablation in liquid [132]; (iv) vapor–liquid–solid growth and chemical vapor deposition [25,40,133]; (v) catalytic immersion method [134]; and (vi) electrochemical and chemical deposition [35,122,135].…”

“…A number of works have also been published on the p-n heterojunction by using a combination of p-type PSi and n-type ZnO [24,35,36,122,125,134], WO 3 [36,129,137,138,139], SnO 2 [122,133], V 2 O 5 [37], and TiO 2 [120]. The sensitivity of these nanocomposites was enhanced in comparison to the bare semiconductors and this can be explained as follows [120]: (a) a reduction in the surface activation energy E a upon the formation of the p-n heterojunction, resulting in increased analyte adsorption; (b) the presence of oxygen species and dangling bonds on PSi/MOx, and as a consequence, more reaction sites on the surface, which improved the adsorption of target molecules.…”

“…The sensitivity of nano-Si/MOx via noble metal deposition [15,36,38,121,139,141,142,143] has also been studied. It a found that noble metal (Ag, Au, Pt, Pd) nanoparticles, imbedded into nano-Si /MOx nanocomposite play an important role in charge generation and significantly increases the quantity of the chemisorption of oxygen ions O − and creates additional active sites, leading to the formation of a deeper depletion region in comparison to that of pure sensors [80,112,115].…”

“…It has been established that Au, Ag, Pd, and Pt nanoparticles deposited over silicon nanopillars or nanowires can be aggregated to “hot spots” and demonstrate a high enhancement factor in SERS-based biosensors with a detection limit less than 10 -12 M [33]. Furthermore, SiNWs and SiNPs in conjunction with metal oxides (TiO 2 , ZnO, WO 3 , F 2 O 3 , TeO 2 ) have shown promising results for gas and biomolecule detection via an electrochemical response with a detection limit of about 1 ppm [34,35,36,37,38]. Recently, a number of new composites have been developed based on SiNWs and SiNPs with sulfides (CdS, MoS 2 ) [39,40] and nitrides (Si 3 N 4 ) [41] that are suitable for sensitive light, humidity, and gas detection due to enhanced absorption and adsorption.…”

Laser‐Induced Colloidal Writing of Organometallic Precursor–Based Repeatable and Fast Pd–Ni Hydrogen Sensor

“…Palladium has been investigated as hydrogen sensor material due to its high dissociative absorption of hydrogen. When coupled with semiconductor material, the dissociate hydrogen might affect the semiconductor electron depletion layer resulting with sensing capabilities …”