{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T20:01:48Z","timestamp":1792008108442,"version":"4.4.0"},"reference-count":39,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2026,1,4]],"date-time":"2026-01-04T00:00:00Z","timestamp":1767484800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>We systematically investigated the optical properties of P-N nanoporous silicon (NPS) diodes fabricated using photoelectrochemical etching and ultrasonic vibration (PEEU), followed by liquid-phase bonding and thermal treatment. Ultrasonic vibration during etching promoted uniform pore formation by enhancing reactant diffusion and suppressing hydrogen bubble accumulation, while laser-induced photocarriers improved etching selectivity, facilitating the formation of NPS with pronounced quantum confinement. The fabricated NPS devices exhibited significantly enhanced photoluminescence (PL) and electroluminescence (EL) properties, with an average external quantum efficiency of 7.3% at a bias of 10 V. Subsequent liquid-phase bonding and thermal annealing further enhanced structural stability and interface quality, resulting in an 180% increase in PL intensity. These results demonstrate that the combination of PEEU with liquid-phase bonding and thermal annealing yields a versatile approach to tailor the optical and electrical properties of P\u2013N porous silicon nanostructures for high-performance light-emitting diodes and quantum-confined silicon photonics, highlighting the critical role of process-induced nanostructures and thermal modifications in device performance.<\/jats:p>","DOI":"10.3390\/mi17010073","type":"journal-article","created":{"date-parts":[[2026,1,5]],"date-time":"2026-01-05T15:28:57Z","timestamp":1767626937000},"page":"73","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["P\u2013N Nanoporous Silicon Fabrication Using Photoelectrochemical Etching and Ultrasonic Vibration and Liquid-Phase Bonding for Optoelectronic Applications"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4127-0950","authenticated-orcid":false,"given":"Chao-Ching","family":"Chiang","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, Asia Eastern University of Science and Technology, New Taipei City 220303, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0439-3537","authenticated-orcid":false,"given":"Philip Nathaniel","family":"Immanuel","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering, Ariel University, Ariel 407000, Israel"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"333","DOI":"10.1002\/j.1538-7305.1956.tb02385.x","article-title":"Electrolytic shaping of germanium and silicon","volume":"35","author":"Uhlir","year":"1956","journal-title":"Bell Syst. Tech. J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1213","DOI":"10.1063\/1.107598","article-title":"Visible photoluminescence from porous silicon: A quantum confinement effect mainly due to holes?","volume":"61","author":"Voos","year":"1992","journal-title":"Appl. Phys. Lett."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"436","DOI":"10.1016\/0169-4332(96)00094-3","article-title":"Progress towards silicon optoelectronics using porous silicon technology","volume":"102","author":"Canham","year":"1996","journal-title":"Appl. Surf. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Abid, H.N., Nayef, U.M., Mutlak, F.A., Muslim, A.M., and Muayad, M.W. (2025). Synthesis of Fe3O4 NPs on porous silicon for photoluminescence-based humidity sensor. Plasmonics.","DOI":"10.1007\/s11468-025-03250-7"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e202400777","DOI":"10.1002\/cssc.202400777","article-title":"Silicon Nanowires via Metal-Assisted Chemical Etching for Energy Storage Applications","volume":"18","author":"Mateen","year":"2025","journal-title":"ChemSusChem"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"5609","DOI":"10.1021\/acsami.4c18296","article-title":"Recent advances of macrostructural porous silicon for biomedical applications","volume":"17","author":"Kang","year":"2025","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Sesu, D.C., Narendran, G., Ramakrishnan, S., Vediappan, K., Esakki Muthu, S., Shanmugan, S., and Kannan, K. (2025). Design and Fabrication of Micro-Electromechanical System (MEMS)-Based \u03bc-DMFC (Direct Methanol Fuel Cells) for Portable Applications: An Outlook. Electrochem, 6.","DOI":"10.3390\/electrochem6020011"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1482877","DOI":"10.1155\/2022\/1482877","article-title":"Porous silicon formation by electrochemical etching","volume":"2022","author":"Kuntyi","year":"2022","journal-title":"Adv. Mater. Sci. Eng."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"856","DOI":"10.1063\/1.104512","article-title":"Porous silicon formation: A quantum wire effect","volume":"58","author":"Lehmann","year":"1991","journal-title":"Appl. Phys. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1046","DOI":"10.1063\/1.103561","article-title":"Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers","volume":"57","author":"Canham","year":"1990","journal-title":"Appl. Phys. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2987","DOI":"10.1063\/1.337750","article-title":"Silicon-to-silicon direct bonding method","volume":"60","author":"Shimbo","year":"1986","journal-title":"J. Appl. Phys."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"840","DOI":"10.1109\/JMEMS.2010.2049731","article-title":"Sequential plasma-activated bonding mechanism of silicon\/silicon wafers","volume":"19","author":"Howlader","year":"2010","journal-title":"J. Microelectromechanical Syst."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Chiang, C.-C., and Immanuel, P.N. (2025). Advanced Techniques for the Fabrication of Nanostructured Porous Silicon Using Photoelectrochemical Etching and Ultrasonic Vibration. Coatings, 15.","DOI":"10.3390\/coatings15020179"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"144","DOI":"10.1007\/BF02375918","article-title":"Supercapacitor devices using porous silicon electrodes","volume":"5","author":"Rowlands","year":"1999","journal-title":"Ionics"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1955","DOI":"10.1007\/s12633-025-03323-6","article-title":"Effect of Etching Duration on the Properties of Porous Silicon and the Characteristics of Photodetectors Based on It","volume":"17","author":"Shbeeb","year":"2025","journal-title":"Silicon"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"323001","DOI":"10.1088\/1361-6463\/ab8769","article-title":"A review: Wafer bonding of Si-based semiconductors","volume":"53","author":"Ke","year":"2020","journal-title":"J. Phys. D Appl. Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2342","DOI":"10.1063\/1.1613812","article-title":"Stabilization of porous silicon electroluminescence by surface passivation with controlled covalent bonds","volume":"83","author":"Gelloz","year":"2003","journal-title":"Appl. Phys. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"063705","DOI":"10.1063\/1.3340834","article-title":"Negative differential resistance in zigzag-edge graphene nanoribbon junctions","volume":"107","author":"Dollfus","year":"2010","journal-title":"J. Appl. Phys."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1016\/j.spmi.2014.12.019","article-title":"Negative differential resistance in porous silicon devices at room temperature","volume":"79","author":"Marin","year":"2015","journal-title":"Superlattices Microstruct."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Ossicini, S., Pavesi, L., and Priolo, F. (2003). Light Emitting Silicon for Microphotonics, Springer Science & Business Media.","DOI":"10.1007\/b13588"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1016\/j.electacta.2009.01.041","article-title":"Synchronization of electrochemical oscillators of S-NDR type","volume":"55","year":"2009","journal-title":"Electrochim. Acta"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"465","DOI":"10.3390\/opt5040035","article-title":"Investigating quantum confinement and enhanced luminescence in nanoporous silicon: A photoelectrochemical etching approach using multispectral laser irradiation","volume":"5","author":"Chiang","year":"2024","journal-title":"Optics"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Chiang, C.-C., and Immanuel, P.N. (2025). Low-Energy Nanoporous Silicon Processing Technology for Next-Generation Optoelectronic Devices. Coatings, 15.","DOI":"10.3390\/coatings15091090"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"3427","DOI":"10.1007\/s10924-021-02142-1","article-title":"Recent progress in silane coupling agent with its emerging applications","volume":"29","author":"Aziz","year":"2021","journal-title":"J. Polym. Environ."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/j.micromeso.2016.01.046","article-title":"Water-based functionalization of mesoporous siliceous materials, Part 1: Morphology and stability of grafted 3-aminopropyltriethoxysilane","volume":"250","author":"Bauer","year":"2017","journal-title":"Microporous Mesoporous Mater."},{"key":"ref_26","first-page":"35","article-title":"Surface functionalisation of porous silicon using 3-Aminopropyl triethoxy silane (APTS)","volume":"2","author":"Singh","year":"2023","journal-title":"Ideal. J. Adv. Res. Progress. Spectr. (IJARPS)"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2158","DOI":"10.1039\/b923890p","article-title":"Wet chemical routes to the assembly of organic monolayers on silicon surfaces via the formation of Si\u2013C bonds: Surface preparation, passivation and functionalization","volume":"39","author":"Ciampi","year":"2010","journal-title":"Chem. Soc. Rev."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2965","DOI":"10.1021\/la960919p","article-title":"Mechanistic aspects of alkylchlorosilane coupling reactions","volume":"13","author":"Rye","year":"1997","journal-title":"Langmuir"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"016003","DOI":"10.1149\/2162-8777\/abdc4b","article-title":"Utilization of low wavelength laser linking with electrochemical etching to produce nano-scale porous layer on p-type silicon wafer with high luminous flux","volume":"10","author":"Immanuel","year":"2021","journal-title":"ECS J. Solid State Sci. Technol."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Pavesi, D.J.L.A.L. (2004). Silicon fundamentals for photonics applications. Silicon Photonics, Springer.","DOI":"10.1007\/978-3-540-39913-1_1"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"31434","DOI":"10.1021\/acsami.9b03583","article-title":"Surface functionalization toward biosensing via free-standing Si\u2013OH bonds on nonoxidized silicon surfaces","volume":"11","author":"Hanisch","year":"2019","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"65012","DOI":"10.1021\/acsami.4c14772","article-title":"Long-Lived Room-Temperature Phosphorescence from Silica Nanoparticles with In Situ Generated Carbonaceous Defects for Blue Organic Light-Emitting Diodes","volume":"16","author":"Han","year":"2024","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Moretta, R., De Stefano, L., Terracciano, M., and Rea, I. (2021). Porous silicon optical devices: Recent advances in biosensing applications. Sensors, 21.","DOI":"10.3390\/s21041336"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"110808","DOI":"10.1016\/j.micromeso.2020.110808","article-title":"Enabling high-porosity porous silicon as an electronic material","volume":"312","author":"Sun","year":"2021","journal-title":"Microporous Mesoporous Mater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"347","DOI":"10.1007\/BF01538334","article-title":"Hydrogen on Si: Ubiquitous surface termination after wet-chemical processing","volume":"60","author":"Pietsch","year":"1995","journal-title":"Appl. Phys. A"},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Issa, A.A., and Luyt, A.S. (2019). Kinetics of alkoxysilanes and organoalkoxysilanes polymerization: A review. Polymers, 11.","DOI":"10.3390\/polym11030537"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"3046","DOI":"10.1149\/1.2220955","article-title":"Developments in luminescent porous Si","volume":"140","author":"Jung","year":"1993","journal-title":"J. Electrochem. Soc."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"388","DOI":"10.1016\/j.apsusc.2015.01.107","article-title":"Progress of porous silicon APTES-functionalization by FTIR investigations","volume":"331","author":"Majoul","year":"2015","journal-title":"Appl. Surf. Sci."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"133102","DOI":"10.1063\/1.5017770","article-title":"Improved quasiballistic electron emission from a nanocrystalline Si cold cathode with a monolayer-graphene surface electrode","volume":"112","author":"Kojima","year":"2018","journal-title":"Appl. Phys. Lett."}],"container-title":["Micromachines"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-666X\/17\/1\/73\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,5]],"date-time":"2026-01-05T15:37:01Z","timestamp":1767627421000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-666X\/17\/1\/73"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,4]]},"references-count":39,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["mi17010073"],"URL":"https:\/\/doi.org\/10.3390\/mi17010073","relation":{},"ISSN":["2072-666X"],"issn-type":[{"value":"2072-666X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,4]]}}}