Micromechanical and structural properties of composite laminate materials used in microelectromechanical technologies

Маtеriјаli kојi sе kоristе u mikrоеlеktrоmеhаničkim sistеmimа (МЕМS) su nајčеšćе u оbliku tаnkih filmоvа kојi su dеpоnоvаni nа supstrаtimа ili fоrmirајu kоmpоzitе sа drugim filmоvimа. Таnkе višеslојnе strukturе imајu spеcifičnа еlеktričnа, mеhаničkа, mаgnеtnа i оptičkа svојstvа i zbоg tоgа imајu pоtеnciјаlа zа širоku primеnu u prоizvоdnji intеgrisаnih kоlа, izrаdi mаgnеtnih glаvа i rаzličitih kоmpоnеnti u МЕМS urеđајimа. Pоrеd tоgа, mаtеriјаli kојi su u оbliku tаnkоg filmа dеpоnоvаni nа supstrаt mоrајu biti kоmpаtibilni sа оsnоvnim mikrоеlеktrоnskim tеhnоlоgiјаmа - litоgrаfiјоm, nаgrizаnjеm, priprеmоm spојеvа, hеmiјskо-mеhаničkim pоlirаnjеm i kоnаčnо mеtоdаmа mоntаžе МЕМS urеđаја. Pоuzdаnоst urеđаја kојi sаdržе оvе višеslојnе strukturе zаvisi оd nеkоlikо fаktоrа uklјučuјući mеhаničku stаbilnоst urеđаја, аdhеziјu slојеvа kаkо mеđusоbnu, tаkо i sа supstrаtоm, аdhеziјu sа mаtеriјаlimа zаštitnih mаski pri nаgrizаnju i pоlirаnju i drugе. Zbоg tоgа su pоtrеbnа dеtаlјnа ispitivаnjа pоuzdаnоsti i kоmpаtibilnоsti mаtеriјаlа kојi ulаzе u sklоp МЕМS urеđаја. Zа pоmеnutu mеhаničku stаbilnоst МЕМS urеđаја bitnа su slеdеćа fizičkо - mеhаničkа svојstvа: аdhеziја nа grаničnim pоvršinаmа slојеvа, mоduli еlаstičnоsti upоtrеblјеnih mаtеriјаlа, tvrdоćа i žilаvоst filmа. Меhаničkа svојstvа tаnkih filmоvа sе rаzlikuјu оd svојstаvа u zаprеmini mаtеriјаlа (bulk mаtеriјаli). Оvо sе mоžе оbјаsniti mikrо/nаnоstrukturоm tаnkih filmоvа kао i timе dа pоstојi uticај supstrаtа nа kојi је film dеpоnоvаn. Uslеd rаzlikа u tеrmо-mеhаničkim svојstvimа supstrаtа i filmа, u tаnkim filmоvimа imа dоstа zаоstаlih nаpоnа nаkоn prоcеsа dеpоnоvаnjа. Тi zаоstаli nаpоni dоvоdе dо trајnih dеfоrmаciја filmа, pа i lоmа kао i dеlаminаciје kоmpоzitnоg mаtеriјаlа ukоlikо su višеslојnа dеpоnоvаnjа u pitаnju. Zbоg tоgа su ispitivаnjа i u еlаstičnој i u plаstičnој оblаsti nаprеzаnjа i dеfоrmаciја јаkо vаžnа zа kаrаktеrizаciјu tаnkih filmоvа. Prеdmеt rаdа оvе disеrtаciје је prоcеsirаnjе lаminаtnih kоmpоzitnih sistеmа mаtеriјаlа Ni i Cu, kао i kаrаktеrizаciја mikrоstrukturе i ispitivаnjе mеhаničkih svојstаvа lаminаtnih kоmpоzitnih sistеmа. Јеdnа оd širоkо rаsprоstrаnjеnih tеhnоlоgiја izrаdе višеslојnih mеtаlnih strukturа kоја је kоmpаtibilnа sа МЕМS tеhnоlоgiјаmа је еlеktrоhеmiјskа dеpоziciја, kоја ćе sе i u оvоm rаdu kоristiti zа fоrmirаnjе mеtаlnih filmоvа. Еlеktrоhеmiјskа dеpоziciја Ni i Cu filmоvа је izvršеnа nа supstrаtimа rаzličitih strukturnih i mеhаničkih svојstаvа (mоnоkristаlni siliciјum rаzličitih оriјеntаciја, pоlikristаlni bаkаr, dеpоnоvаni slој niklа dоvоlјnо vеlikе dеblјinе dа sе pоnаšа kао sаmоstаlnа pоdlоgа). Prоmеnоm pаrаmеtаrа еlеktrоhеmiјskе dеpоziciје (tеmpеrаturа, gustinа struје, vrеmе dеpоziciје), dоbiјајu sе filmоvi rаzličitе dеblјinе i mikrоstrukturе, štо zа pоslеdicu imа rаzličitа mеhаničkа svојstvа. Dеblјinе pојеdinаčnih slојеvа kоmpоzitа su mаlе pа је i ukupnа dеblјinа kоmpоzitа mаlа (2-10μm). Zbоg mаlе dеblјinе višеslојnih kоmpоzitа, uticај prisustvа supstrаtа i njеgоvе mеhаničkе kаrаktеristikе sе nе mоgu zаnеmаriti. Zа kаrаktеrizаciјu strukturе dоbiјеnih lаminаtnih kоmpоzitnih mаtеriјаlа prеdviđеnе su mеtоdе оptičkе mikrоskоpiје, skеnirајućе аtоmskе mikrоskоpiје (АFМ) kао i skеnirајućе еlеktrоnskе mikrоskоpiје (SЕМ). Nајčеšćе kоrišćеn mеtоd zа tеstirаnjе mеhаničkih svојstаvа sistеmа film-supstrаt је mеtоd utiskivаnjа. Ispitivаnjа mеhаničkih svојstаvа kоmpоzitnih sistеmа u оvој disеrtаciјi оbаvlјеnо је mеtоdоm utiskivаnjа pо Vikеrsu. Оvај mеtоd је, nаrоčitо sа оptеrеćеnjimа u mikrо оpsеgu, pоkаzао svојu prеdnоst pri оdrеđivаnju nеkih mеhаničkih svојstаvа (tvrdоćа i mоdul еlаstičnоsti) јеdnоslојnih tаnkih filmоvа. Kаdа је film višеslојаn (kоmpоzitni film), mоrа sе vоditi rаčunа о mеđusоbnоm uticајu mеhаničkih i strukturnih svојstаvа svаkе kоmpоnеntе kоmpоzitа. U оvоm istrаživаnju, urаđеni su tеstоvi mikrоutiskivаnjа pо Vikеrsu nа pоdlоgаmа i fоrmirаnim јеdnоslојnim i kоmpоzitnim sistеmimа pri rаzličitim оptеrеćеnjimа. Izmеrеnа vrеdnоst mikrоtvrdоćе kоја sе nаzivа "kоmpоzitnоm mikrоtvrdоćоm" је kоmplеksnа, јеr zаvisi оd rеlаtivnе dubinе utiskivаnjа i pојеdinаčnih mеhаničkih svојstаvа filmоvа i supstrаtа. Моdеli prеdviđаnjа tvrdоćе su rаzviјеni u cilјu оdrеđivаnjа аpsоlutnе tvrdоćе tаnkоg filmа iz stаndаrdnih tеstоvа mikrоutiskivаnjа (Јеnsеn-Hоgmаrk, Bаrnеt-Rikеrbi, Šikо-Lеzаž, Kоrsunski). Zа оdrеđivаnjе tvrdоćе filmа u višеslојnim sistеmimа Ni i Cu nа krupnоzrnоm supstrаtu bаkrа (sistеm tvrdоg filmа nа mеkоm supstrаtu), primеnjеn је dеskriptivni mоdеl Kоrsunskоg, kојi dаје zаdоvоlјаvајućе rеzultаtе fitоvаnjа.Materials and structures with small-scale dimensions do not behave in the same manner as their bulk counterparts. This became significantly important when we deal with thin films which are routinely employed as components in microelectromechanical systems (MEMS). Thin multilayered structures have specific electric, mechanical, magnetic and optical properties and because of that have great potential for applications in fabrication of different MEMS components. Thin film materials together with their substrates have to be compatible with fundamental MEMS technologies – litography, deposition methods, etching, mechanical and chemical polishing, etc. This thesis is mainly confronted with the problem of structural and mechanical characterization of multilayered composite films. Multilayered composite systems of alternately electrodeposited nanocrystalline Cu and Ni films on cold-rolled microcrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The mechanical properties of the composite systems were characterized using Vickers microhardness testing. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. After the mechanical testing, samples were prepared for the examination by metalographic microscopy. Topographic details were investigated by means of atomic force microscope operating in non-contact mode. Composite hardness models of Jonsson-Hogmark, Burnett-Rickerby, Chicot-Lesage and Korsunsky were applied to the experimental data in order to determine film hardness. The applicability of mentioned models is critically tested on two types of composite systems: hard film on soft substrate and soft film on hard substrate. Korsunsky model was chosen and applied for the multilayered composite systems Ni/Cu on polycrystalline Cu substrate. These systems were considered as "hard film on a soft substrate" type of composite systems

Influence of parameters of the pulsating current (PC) regime on morphological, structural and hardness characteristics of copper coatings electrodeposited on Si(111)

Electrodeposition of Cu was performed on Si(111) by the pulsating current (PC) regime in the range of the average current densities (jav) between 15 and 70 mA cm-2 . The selected values of the average current densities were attained by varying either pause duration (tp: 28.3, 15, 7.5 and 5 ms, i.e. jav: 15, 25, 40 and 50 mA cm-2 for the constant values of deposition pulse of 5 ms and current density amplitude (jA) of 100 mA cm-2) or amplitude of the current density (jA: 120 and 140 mA cm-2 , i.e. jav: 60 and 70 mA cm-2 for the constant values of deposition pulse of 5 ms and pause duration of 5 ms). Morphological and structural characteristics of the obtained coatings were examined by scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD), respectively. With increasing the average current density, morphologes of the coatings changed from those with large and well defined crystal grains obtained at jav of 15 mA cm-2 (the dominant effect of activation control) to fine-grained obtained at jav of 50 mA cm-2 (the mixed activation-diffusion control) and those with globules when diffusion becomes a dominant process (jav = 70 mA cm-2). The minimum roughness showed the Cu coating obtained at jav of 50 mA cm-2 . Simultaneously, crystal structure changed from the strong (220) to the strong (111) preferred orientation with increasing average current density. The change of surface morphology was discussed by the effect of applied parameters of the PC regime on the type of electrodeposition control, while change in crystal orientation of produced coatings was explained by various rates of growth on various crystal planes. Hardness analysis of the produced coatings was performed by application of the Chicot-Lesage (C-L) composite hardness model. By application of this model, the relative indentation depth (RID; where RID = h/d; h is an indentation depth, and d is a thickness of coating) of 0.14 was established as the limiting value separating the area of the absolute hardness of the Cu coatings (RID < 0.14) from the area in which application of the C-L model is necessary for a determination of the absolute hardness of coatings (RID > 0.14). For RID < 0.14, the measured composite hardness corresponded to the absolute hardness of the coating

Effect of concentration pigment particles on microstructure of the metal matrix copper composite coatings

This research focuses on the synthesis and characterization of composite coatings via electrochemical route with co-deposition pigments. For that reason, the effect of adding yellow green phosphorescent pigment on microstructural evaluation of the Cu/pigment composite systems has been investigated.Second International Conference on Electron Microscopy of Nanostructures ELMINA 2022, August 22nd-26th, 2022, Belgrade, Serbia

Одређивање апсолутне тврдоће електролитички добијених превлака бакра применом Chicot-Lesage композитног модела тврдоће

In this study, a novel procedure, based on application of the Chicot–Lesage (C–L) composite hardness model, was proposed for the determination of an absolute hardness of electrolytically produced copper coatings. The Cu coatings were electrodeposited on the Si(111) substrate by the pulsating current (PC) regime with a variation of the following parameters: the pause duration, the current density amplitude and the coating thickness. The topography of produced coatings was characterized by atomic force microscope (AFM), while a hardness of the coatings was examined by Vickers microindentation test. Applying the C–L model, the critical relative indentation depth (RID)c of 0.14 was determined, which is independent of all examined parameters of the PC regime. This RID value separated the area in which the composite hardness of the Cu coating corresponded to its absolute hardness (RID <0.14) from the area in which the application of the C–L model was necessary for a determination of the absolute coating hardness (RID ≥ 0.14). The obtained value was in a good agreement with the value already published in the literature.Предложен je нови поступак заснован на примени Chicot–Lesage (C–L) композитног модела тврдоће за одређивање апсолутне тврдоће електролитички добијених превлака бакра. Превлаке бакра су електрохемијски исталожене на силицијуму (111) оријентације режимом пулсирајуће струје варирањем следећих параметара: трајање паузе, амплитудна густина струје и дебљина превлаке. Топографија произведених превлака је окарактерисана микроскопијом атомских сила, док је тврдоћа превлака испитивана Викерсовим тестом утискивања. Применом C–L композитног модела тврдоће, одређена је критична релативна дубина утискивања (RID), од 0,14, која је независна од свих испитиваних параметара режима пулсирајуће струје. Ова вредност раздваја област у којој композитна тврдоћа превлаке може да се изједначи са њеном апсолутном тврдоћом (RID << 0,14) од области у којој је неопходно применити C–L модел за одређивање апсолутне тврдоће превлаке (RID ≥ 0,14). Добијена вредност RID показује добро слагање са вредностима публикованим у литератури

Morphology, structure and hardness of electrolytically produced copper coatings

Poster presented at: 4th International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, June, 30th-July, 02nd, Sarajevo, Bosnia and HerzegovinaAbstract: [https://cer.ihtm.bg.ac.rs/handle/123456789/5213

Influence of intensity of ultrasound on morphology and hardness of copper coatings obtained by electrodeposition

The influence of various intensities of ultrasound applied for the electrolyte stirring on morphological and mechanical characteristics of electrolytically produced copper coatings has been investigated. The copper coatings produced by the galvanostatic regime of the electrodeposition from the basic sulphate electrolyte and the electrolyte with added levelling/brightening additives at the low temperature were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques (surface morphology and topography, respectively) and by Vickers microindentation (hardness). The roughness of coatings increased with the increasing intensity of ultrasound, indicating that morphology of the coatings worsened with the enhanced application of ultrasonic waves. This is attributed to the strong effect of ultrasound on hydrodynamic conditions in the near-electrode layer, which is manifested by the increase of share of the activation control in the mixed activation-diffusion control of electrodeposition with increasing the intensity of ultrasound. The concept of "effective overpotential" originally proposed to explain a change of surface morphology in the conditions of vigorous hydrogen evolution is also applicable for a change of morphology of Cu coatings under the imposed effect of ultrasonic waves. Hardness analysis of the coatings showed that an intensity of applied ultrasound did not have any significant effect on the hardness, especially for the Cu coatings produced from the basic sulphate electrolyte

Optimization of electrodeposition parameters to improve composite hardness of nickel coatings on brass substrate for varying film thicknesses and applied indentation loads

In this investigation, nickel coatings were electrodeposited on brass substrate. The effects of electrodeposition process parameters such as, current density and deposition time (coatings thickness), on surface morphology and composite hardness values were studied. The value of the measured composite hardness by Vickers microindentation technique of the selected “hard film on soft substrate” composite system type depends on the applied indentation loads. For this reason, the microindentation loads are also included in the analysis. According to the experiment plan obtained by Design-Expert software, nickel coating has been produced on the brass cathode using galvanostatic regime (DC) with magnetic stirring of the electrolyte. The nickel sulphamate electrolyte with saccharine additive was used for Ni electrodeposition. Then, response surface methodology (RSM) was used to establish an adequate mathematical model. Subsequently, a mathematical model was developed to weight the effects of each input parameters (coating thickness, current density and indentation load) on the output parameter (composite hardness) of electrodeposited nickel coatings on brass substrate. According to the obtained results, the coating thickness and indentation load greatly influenced resulting composite hardness. On the other hand, coating current density primarily influenced microstructure and surface roughness. The topographic modification of the Ni coating surface depending on the post-treatment (mechanical and chemical) after deposition was studied using AFM microscopy

Application of copper electrodeposition processes in visualization of latent fingerprints obtained on various substrates

In this study, a basic sulfate electrolyte for electrochemical copper deposition and a sulfate electrolyte with additives to improve coating quality were used. It has been shown that for the visualization of latent fingerprints, it is better to use an electrolyte without additives. The use of electrolytes with additives has not been shown to be adequate for these purposes due to the effect of filling fingerprint ridges and reducing contrast

Development of latent fingermarks by electrochemical deposition of nickel on brass surfaces

Introduction/purpose of the research: Latent fingermarks can be found on the crime scene on various surfaces and made visible by different forensic methods. As this evidence can often be found on brass surfaces (ammunition casings, decorative items, etc.) the paper discusses the possibilities of applying electrochemical deposition of nickel on brass. The condition for the application of this technique is the existence of a conductive substrate. Fatty components of latent fingermarks have insulating properties and prevent the electrodeposition process. Methods: Experimental thin rectangular pieces of brass foil were used as substrates for latent fingermarks. Samples were degreased in acetone and ethyl alcohol, rinsed in deionized water, and dried in a stream of compressed air before leaving the fingermarks. To enhance the presence of sweat on friction ridges, the hand was placed in the silicone glove for five minutes. A slight touch of the index finger was left on the tiles. Fingermarks were developed on brass samples by fingerprint powder and the electrochemical deposition of nickel on another brass surface simultaneously. In order to obtain the best possible evidence, the parameters affecting the deposition rate (current density, deposition time) were changed until a clear fingermark was obtained. Results: The fingermarks were compared visually using a magnifying glass with illumination to observe the contrast between the papillary lines and the interpapillary space and the characteristic details (minutiae). The optimal results were achieved with the current density (deposition rate) of 50mA/cm2 for 10s. Conclusion: Electrochemical deposition of nickel on brass is an applicable technique for developing latent fingermarks with certain limitations

Morphology, structure and hardness of electrolytically produced copper coatings

Influence of various parameters of electrodeposition, such as type of cathode, composition of the electrolyte and thickness of the coating, on morphology, structure and hardness of copper coatings has been investigated.Poster: [https://cer.ihtm.bg.ac.rs/handle/123456789/5214