{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:16:13Z","timestamp":1760141773645,"version":"build-2065373602"},"reference-count":42,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2025,9,30]],"date-time":"2025-09-30T00:00:00Z","timestamp":1759190400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Materials"],"abstract":"<jats:p>This study investigated the effects of silver doping, natural ageing, and thermal-induced oxidation on the surface chemistry, morphology, and thermal performance of copper thin films. Ag is used as a doping element in Cu because, in bulk materials it usually refines microstructures, leading to increased hardness and mechanical strength through mechanisms such as solid solution strengthening and twinning. In this work was also used due to its oxidation resistance. Thin films of pure and silver-doped copper (Cu_2Ag and Cu_4Ag) were deposited by RF magnetron sputtering and characterized as-deposited, naturally aged, at room temperature and humidity for one year, and thermally treated at 200 \u00b0C, in air. The characterization included X-ray photoelectron spectroscopy (XPS), Atomic Force microscopy (AFM), and thermal analysis, specifically thermal conductivity (\u03bb), thermal diffusivity (\u03b1), and thermal capacity (\u03c1.Cp). Surface XPS analysis revealed changes in copper and silver oxidation states after natural aging and annealing. AFM revelead that the incorporation of silver and heat treatment altered the surface roughness and morphology. Thermal analysis found that for lower silver concentrations, the thermal conductivity increased, but aging and annealing had varying effects depending on the silver content. The Cu_4Ag film showed the best thermal stability after natural ageing. Overall, the results suggest that carefully controlled silver doping can enhance the thermal stability of copper thin films for applications where aging is a concern, such as microelectronics.<\/jats:p>","DOI":"10.3390\/ma18194562","type":"journal-article","created":{"date-parts":[[2025,9,30]],"date-time":"2025-09-30T15:38:55Z","timestamp":1759246735000},"page":"4562","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Topographic, Thermal and Chemical Characterization of Oxidized Cu and Cu-Ag Thin Films"],"prefix":"10.3390","volume":"18","author":[{"given":"Maria C.","family":"Carrupt","sequence":"first","affiliation":[{"name":"CEMMPRE, Department of Mechanical Engineering, University of Coimbra, 3030-788 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6784-6540","authenticated-orcid":false,"given":"Ana M.","family":"Ferraria","sequence":"additional","affiliation":[{"name":"iBB, Interdisciplinary Complex, Instituto Superior T\u00e9cnico, University of Lisbon, 1049-001 Lisbon, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6179-9296","authenticated-orcid":false,"given":"Ana P.","family":"Serro","sequence":"additional","affiliation":[{"name":"CQE\u2014Instituto Superior T\u00e9cnico, Department of Chemical Engineering, University of Lisbon, 1349-017 Lisbon, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1588-0640","authenticated-orcid":false,"given":"Ana P.","family":"Piedade","sequence":"additional","affiliation":[{"name":"CEMMPRE, Department of Mechanical Engineering, University of Coimbra, 3030-788 Coimbra, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"489","DOI":"10.1016\/j.apsusc.2016.04.109","article-title":"Polymer\/metal nanocomposite coating with antimicrobial activity against hospital isolated pathogen","volume":"379","author":"Carvalho","year":"2016","journal-title":"Appl. Surf. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Oliveira, B.M.C., Santos, R.F., Piedade, A.P., Ferreira, P.J., and Vieira, M.F. (2022). Co-W Barrier Layers for Metallization of Copper Interconnects: Thermal Performance Analysis. Nanomaterials, 12.","DOI":"10.3390\/nano12101752"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"105103","DOI":"10.1088\/0957-4484\/18\/10\/105103","article-title":"In vitro behaviour of nanocrystalline silver-sputtered thin films","volume":"18","author":"Piedade","year":"2007","journal-title":"Nanotechnology"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"7188","DOI":"10.1021\/acsami.0c20539","article-title":"Alkali Dispersion in (Ag, Cu)(In, Ga) Se2 Thin Film Solar Cells\u2014Insight from Theory and Experiment","volume":"13","author":"Aboulfadl","year":"2021","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"21243","DOI":"10.1021\/acsami.7b03944","article-title":"Elemental Precursor Solution Processed (Cu1\u2212)","volume":"9","author":"Qi","year":"2017","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"5455","DOI":"10.1021\/acsami.7b14929","article-title":"Structural and Solar Cell Properties of a Ag-Containing Cu2 ZnSnS4 Thin Film Derived from Spray Pyrolysis","volume":"10","author":"Nguyen","year":"2018","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2300670","DOI":"10.1002\/solr.202300670","article-title":"A Comprehensive Review on the Recent Strategy of Cation Substitution in CZTS (Se) Thin Films to Achieve Highly Efficient Kesterite Solar Cells","volume":"7","author":"Kangsabanik","year":"2023","journal-title":"Sol. RRL"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1016\/j.solmat.2018.04.002","article-title":"Seed-layer-free growth of ultra-thin Ag transparent conductive fi lms imparts fl exibility to polymer solar cells","volume":"184","author":"Huang","year":"2018","journal-title":"Sol. Energy Mater. Sol. Cells"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"9988","DOI":"10.1021\/acs.chemmater.3c01837","article-title":"Cu\/Ag\u2013Sb\u2013I Rudorffite Thin Films for Photovoltaic Applications","volume":"35","author":"Hooijer","year":"2023","journal-title":"Chem. Mater."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"167980","DOI":"10.1016\/j.ijleo.2021.167980","article-title":"Efficiency enhancement of nano structured Cu2O:Ag\/laser etched silicon-thin films fabricated via vacuum thermal evaporation technique for solar cell application","volume":"247","author":"Nihad","year":"2021","journal-title":"Optik"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"180","DOI":"10.1016\/j.mee.2009.07.010","article-title":"Microelectronic Engineering Electroplating of Cu (Ag) thin films for interconnect applications","volume":"87","author":"Strehle","year":"2010","journal-title":"Microelectron. Eng."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"140141","DOI":"10.1016\/j.tsf.2023.140141","article-title":"Highly flexible and transparent electrodes for high-performance thin-film heaters with nanostructured micromesh Cu\u2014Ag ultrathin films","volume":"787","author":"Han","year":"2023","journal-title":"Thin Solid Film."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Pinho, A.C., Morais, P.V., Pereira, M.F., and Piedade, A.P. (2025). Changes in the Antibacterial Performance of Polymer-Based Nanocomposites Induced by Additive Manufacturing Processing. Polymers, 17.","DOI":"10.3390\/polym17020171"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"102897","DOI":"10.1016\/j.surfin.2023.102897","article-title":"Evolutionary selection growth of silver films for low-loss nanophotonic devices","volume":"39","author":"Baburin","year":"2023","journal-title":"Surf. Interfaces"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"101093","DOI":"10.1016\/j.coco.2022.101093","article-title":"Interconnected network of Ag and Cu in bioplastics for ultrahigh electromagnetic interference shielding efficiency with high thermal conductivity","volume":"30","author":"Kim","year":"2022","journal-title":"Compos. Commun."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"115702","DOI":"10.1088\/1361-648X\/ac4074","article-title":"Stabilizing effects of Ag doping on structure and thermal stability of FeN thin films","volume":"34","author":"Niti","year":"2022","journal-title":"J. Phys. Condens. Matter"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Carrupt, M.C., Serro, A.P., and Piedade, A.P. (2024). Influence of the Ag Content on the Natural and Thermal Induced Oxidation of Cu Thin Films. Materials, 17.","DOI":"10.3390\/ma17235974"},{"key":"ref_18","unstructured":"Haynes, W.M., Lide, D.R., and Bruno, T.J. (2014). CRC Handbook of Chemistry and Physics, Taylor & Francis Group. [95th ed.]."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1101","DOI":"10.1021\/jp076981k","article-title":"Oxidation of polycrystalline copper thin films at ambient conditions","volume":"112","author":"Platzman","year":"2008","journal-title":"J. Phys. Chem. C"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1016\/j.jallcom.2016.12.246","article-title":"SERS enhancement, sensitivity and homogeneity studies on bi-metallic Ag-Cu films through tuning of broad band SPR towards red region","volume":"698","author":"Pal","year":"2017","journal-title":"J. Alloys Compd."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"209","DOI":"10.1016\/j.apsusc.2015.12.003","article-title":"Slow oxidation kinetics in an epitaxial copper(1 0 0) film","volume":"363","author":"Timalsina","year":"2016","journal-title":"Appl. Surf. Sci."},{"key":"ref_22","first-page":"163","article-title":"Theory of the oxidation of metals Some interactions of gases with metals and crystalline solids","volume":"12","author":"Ramsey","year":"1949","journal-title":"Rep. Prog. Phys."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1016\/S0040-6090(03)00541-8","article-title":"Effect of substrate bias voltage on the purity of Cu films deposited by non-mass separated ion beam deposition","volume":"434","author":"Lim","year":"2003","journal-title":"Thin Solid Film."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"170","DOI":"10.1002\/sia.2985","article-title":"Characterization of silver selenide thin films grown on Cr-covered Si substrates","volume":"41","author":"Mohanty","year":"2009","journal-title":"Surf. Interface Anal."},{"key":"ref_25","unstructured":"Springer Science & Business Media (2007). Silver Metallization: Stability and Reliability, Springer Sciene + Business Media, LLC."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Hsieh, J., and Hung, S. (2016). The effect of cu: Ag atomic ratio on the properties of sputtered cu-ag alloy thin films. Materials, 9.","DOI":"10.3390\/ma9110914"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"155306","DOI":"10.1088\/0022-3727\/41\/15\/155306","article-title":"Texture and surface morphology evolution of Ag(Cu) layers on indium tin oxide thin films","volume":"41","author":"Han","year":"2008","journal-title":"J. Phys. D Appl. Phys."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"036101","DOI":"10.1063\/1.2761822","article-title":"Improved surface morphology and texture of Ag films on indium tin oxide via Cu additions","volume":"102","author":"Han","year":"2007","journal-title":"J. Appl. Phys."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"100650","DOI":"10.1016\/j.surfin.2020.100650","article-title":"Stereometric and fractal analysis of sputtered Ag-Cu thin films","volume":"21","author":"Matos","year":"2020","journal-title":"Surf. Interfaces"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"024106","DOI":"10.1063\/1.3675611","article-title":"Evolution of nanoscale roughness in Cu\/SiO2 and Cu\/Ta interfaces","volume":"100","author":"Warren","year":"2012","journal-title":"Appl. Phys. Lett."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1506","DOI":"10.1007\/s11664-001-0166-0","article-title":"Effect of annealing on the surface microstructural evolution and the electromigration reliability of electroplated Cu films","volume":"30","author":"Kang","year":"2001","journal-title":"J. Electron. Mater."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"083548","DOI":"10.1063\/1.2800998","article-title":"Copper enhanced (111) texture in silver thin films on amorphous SiO2","volume":"102","author":"Zoo","year":"2007","journal-title":"J. Appl. Phys."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"838","DOI":"10.1116\/1.3319349","article-title":"Synergistic Ag (111) and Cu (111) texture evolution in phase-segregated Cu1\u2212xAgx magnetron sputtered composite thin films","volume":"28","author":"Filoti","year":"2010","journal-title":"J. Vac. Sci. Technol. A Vac. Surf. Film."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"044305","DOI":"10.1063\/1.2968440","article-title":"Surface morphological evolution during annealing of epitaxial Cu(001) layers","volume":"104","author":"Purswani","year":"2008","journal-title":"J. Appl. Phys."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s11082-021-02942-8","article-title":"Influence of deposition time on the optical and morphological properties of silver\u2013copper thin films: Experimental and statistical studies","volume":"53","author":"Noorbakhsh","year":"2021","journal-title":"Opt. Quantum Electron."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"12953","DOI":"10.1021\/acs.jpcc.5c00736","article-title":"Surface Modification of CuO\/Cu2O\/Cu Composite Particles with Ag by Pulsed Laser Irradiation of Suspension and Their Antimicrobial Potentia","volume":"129","author":"Shakeri","year":"2025","journal-title":"J. Phys. Chem. C"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"244905","DOI":"10.1063\/1.4812584","article-title":"Structural and optical properties of Ag-doped copper oxide thin films on polyethylene napthalate substrate prepared by low temperature microwave annealing","volume":"113","author":"Das","year":"2013","journal-title":"J. Appl. Phys."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"De Carlo, I., Baudino, L., Klapetek, P., Serrapede, M., Michieletti, F., De Leo, N., Pirri, F., Boarino, L., Lamberti, A., and Milano, G. (2023). Electrical and Thermal Conductivities of Single CuxO Nanowires. Nanomaterials, 13.","DOI":"10.3390\/nano13212822"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1534","DOI":"10.1021\/acs.jpcc.3c07694","article-title":"Study on the Anharmonic Interaction in Negative Thermal Expansion Compounds Ag2O and Cu2O by Three-Phonon Scattering","volume":"128","author":"Wang","year":"2024","journal-title":"J. Phys. Chem. C"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"73","DOI":"10.5802\/crphys.162","article-title":"Vibrations and Heat Transfer in Glasses: The Role Played by Disorder","volume":"24","author":"Tanguy","year":"2024","journal-title":"Comptes Rendus Phys."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"e1804097","DOI":"10.1002\/adma.201804097","article-title":"Interfacial Defect Vibrations Enhance Thermal Transport in Amorphous Multilayers with Ultrahigh Thermal Boundary Conductance","volume":"30","author":"Giri","year":"2018","journal-title":"Adv. Mater."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"177801","DOI":"10.1016\/j.jallcom.2024.177801","article-title":"Effects of the grain size and orientation of Cu on the formation and growth behavior of intermetallic compounds in Sn-Ag-Cu solder joints","volume":"1010","author":"Han","year":"2025","journal-title":"J. Alloys Compd."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/18\/19\/4562\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T04:25:19Z","timestamp":1760070319000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/18\/19\/4562"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,9,30]]},"references-count":42,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2025,10]]}},"alternative-id":["ma18194562"],"URL":"https:\/\/doi.org\/10.3390\/ma18194562","relation":{},"ISSN":["1996-1944"],"issn-type":[{"type":"electronic","value":"1996-1944"}],"subject":[],"published":{"date-parts":[[2025,9,30]]}}}