{"title":"Improving the electrical and structural stability of highly piezoresistive nickel–carbon sensor thin films","authors":"G. Schultes, M. Cerino, A. Lellig, M. Koch","doi":"10.5194/jsss-11-137-2022","DOIUrl":null,"url":null,"abstract":"Abstract. The family of sputter deposited granular metal-based\ncarbon-containing sensor films is known for their high sensitivity\ntransforming force-dependent strain into electrical resistance change. Among\nthem nickel–carbon thin films possess a gauge factor of up to 30, compared\nto only 2 for traditional sensor films of metal alloys. This high\nsensitivity is based on disordered interparticle tunneling through barriers\nof graphite-like carbon walls between metal–carbon particles of columnar\nshape. Force and pressure sensors would benefit a lot from the elevated\npiezoresistivity. A disadvantage, however, is a disturbing temporal creep\nand drift of the resistance under load and temperature. This contribution\nshows how to stabilize such sensor films. A significant stabilization is\nachieved by partially replacing nickel with chromium, albeit at the expense\nof sensitivity. The more chromium used in these NixCr1−x-C layers,\nthe higher the optimum annealing temperature can be selected and the better\nthe electrical stabilization. A good compromise while maintaining\nsensitivities well above the standard of 2 is identified for films with\nx=0.5 to 0.9, stabilized by optimized temperature treatments. The\nstabilizing effect of chromium is revealed by transmission electron\nmicroscopy with elemental analysis. The post-annealing drives segregation\nprocesses in the layer material. While the interior of the layer is depleted\nof chromium and carbon, boundary layers are formed. Chromium is enriched\nnear the surface boundary, oxidized in air and forms chromium-rich oxide\nsub-layers, which are chemically very stable and protect against further\nreactions and corrosion. As a result, creep and drift errors are greatly\nreduced, so that the optimized sensor coatings are now suitable for\nwidespread use.\n","PeriodicalId":17167,"journal":{"name":"Journal of Sensors and Sensor Systems","volume":null,"pages":null},"PeriodicalIF":0.8000,"publicationDate":"2022-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Sensors and Sensor Systems","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.5194/jsss-11-137-2022","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"INSTRUMENTS & INSTRUMENTATION","Score":null,"Total":0}
引用次数: 0
Abstract
Abstract. The family of sputter deposited granular metal-based
carbon-containing sensor films is known for their high sensitivity
transforming force-dependent strain into electrical resistance change. Among
them nickel–carbon thin films possess a gauge factor of up to 30, compared
to only 2 for traditional sensor films of metal alloys. This high
sensitivity is based on disordered interparticle tunneling through barriers
of graphite-like carbon walls between metal–carbon particles of columnar
shape. Force and pressure sensors would benefit a lot from the elevated
piezoresistivity. A disadvantage, however, is a disturbing temporal creep
and drift of the resistance under load and temperature. This contribution
shows how to stabilize such sensor films. A significant stabilization is
achieved by partially replacing nickel with chromium, albeit at the expense
of sensitivity. The more chromium used in these NixCr1−x-C layers,
the higher the optimum annealing temperature can be selected and the better
the electrical stabilization. A good compromise while maintaining
sensitivities well above the standard of 2 is identified for films with
x=0.5 to 0.9, stabilized by optimized temperature treatments. The
stabilizing effect of chromium is revealed by transmission electron
microscopy with elemental analysis. The post-annealing drives segregation
processes in the layer material. While the interior of the layer is depleted
of chromium and carbon, boundary layers are formed. Chromium is enriched
near the surface boundary, oxidized in air and forms chromium-rich oxide
sub-layers, which are chemically very stable and protect against further
reactions and corrosion. As a result, creep and drift errors are greatly
reduced, so that the optimized sensor coatings are now suitable for
widespread use.
期刊介绍:
Journal of Sensors and Sensor Systems (JSSS) is an international open-access journal dedicated to science, application, and advancement of sensors and sensors as part of measurement systems. The emphasis is on sensor principles and phenomena, measuring systems, sensor technologies, and applications. The goal of JSSS is to provide a platform for scientists and professionals in academia – as well as for developers, engineers, and users – to discuss new developments and advancements in sensors and sensor systems.