Microelectronic sensor of elemental mercury (Hg) in gas phase

Cilj ove disertacije je razvoj mikroelektronskog adsorpcionog senzora i osvajanje tehnologije njegove proizvodnje za potrebe praćenja aero zagañenja, zaštite životne sredine i primene u industrijskim procesima. Senzor je izrañen pomoću opreme za mikroelektroniku dostupnu na IHTM CMTM u Beogradu i testiran na aparaturi koja može veoma precizno da zadaje kocentraciju živine pare u komori senzora. Senzor je testiran na koncentracije žive u atmosferi čistog azota u rasponu od 4 do 200 μg/m3. Radna struja senzora u svim eksperimentima je držana na 10 mA pomoću strujnog izvora, tj. senzor je radio u modu konstantne struje. Ulazni napon je bio (5,0 ± 0,1) V što odgovara otporu Vitstonovog mosta senzora od (500 ± 10) . Senzor je takoñe testiran na koncentraciju od 14 g/m3 što odgovara naponu pare žive pri temperaturi od 20 0C. Kompletan ciklus merenja i odgrevanja senzora je prikazan sa objašnjenjem mogućnosti praćenja procesa odgrevanja preko izlaznog napona senzora. U disertaciji je dat metod očitavanja senzora za dobijanje maksimalne osetljivosti. U ovom postupku očitavanja senzora moguće je prag detekcije sniziti ispod 0,18 μg/m3 što je pet puta manje or ranije objavljenih vrednosti i omogućava upotrebu senzora za praćenje malih vrednosti zagañenja. U okviru ove disertacije senzor je unapreñen u smislu nove procedure očitavanja izlaznog signala koja omogućava kontinualno (u svakom trenutku vremena) praćenje koncentracije žive u gasnoj fazi. Prehodni pokušaji da se ostvari kontinualno očitavanje ovakvog senzora zasnivali su se na dodavanju difuzionog filtera i pravljenju gradijenta koncentracije ispred površine senzora. U ovoj disertaciji pokazano je da je poznavanje trenutne vrednosti izlaznog napona i priraštaja izlaznog napona u vremenu dovoljno za kontinualno očitavanje senzora. Na ovakav način rešen je ključni problem za praktičnu primenu senzora. Tehnološki detalji izrade senzora su unapreñeni uvoñenjem novog postupka izrade sa manjim brojem koraka što pojednostavljuje i snižava cenu proizvodnje. Svi detalji izrade su objašnjeni i na osnovu ovih objašnjenja Milija Sarajlić Mikroelektronski senzor elementarne žive Rezime moguće je u potpunosti reprodukovati proces izrade senzora uz posedovanje odgovarajuće opreme. Disertacija daje pregled mernih metoda i senzora do sada poznatih za merenje koncentracije živine pare u vazduhu. Poseban akcenat je stavljen na senzore koji funkcionišu po principu površinske adsorpcije. Ovo iz razloga što senzor razvijen u okviru teze funkcioniše po istom principu. Opšti podaci o fizičko-hemijskim osobinama žive su dati a takoñe i uticaj žive kao zagañivača na ljudsku okolinu. Poseban osvrt dat je na zakonsku regulativu o zaštiti ljudi na radu i u svakodnevnim uslovima. Moguće je pojednostaviti izradu senzora i proizvesti ga pomoću opreme koja je već dostupna za izradu mikroelektronskih komponeneti sa najsitnijim detaljima od 20 μm. Senzor ima osetljivost dovoljno veliku da može da registruje mala zagañenja životne okoline, daleko ispod propisanih zakonskih maksimuma. Takoñe, sa novom procedurom kontinualnog očitavanja senzor se može iskoristiti za praćenje trenutnih promena koncentracije živine pare u atmosferi.The goal of this work was to develop an adsorption based microelectronic sensor along with the technology for its production. The sensor is intended for environmental pollution monitoring and applications in the industrial processes. The sensor was fabricated by the equipment available at the IHTM CMTM, Belgrade, Serbia and tested on a set-up which allows for precise tuning of mercury vapor concentration in the sensor chamber. The sensor was tested for different concentrations of mercury vapor in the range from 4 to 200 μg/m3. Mercury vapor was mixed with pure nitrogen and by this mixing various concentrations were achieved. The operating current in all of the experiments was held at 10 mA. The sensor was operating in the constant current mode. The input voltage was (5 ± 0,1) V which corresponds to a Wheatstone bridge resistance of (500 ± 10) . Together with this, the sensor is tested on a concentration of 14 g/m3 which corresponds to the mercury vapor pressure on 20 0C. The complete cycle of the sensor measurement and restoration is presented. Within this thesis, a method for the sensor readout for maximum sensitivity is developed. The readout procedure for the maximum sensitivity lowers the detection threshold below the value of 0.18 μg/m3 which is five times lower than the previously reported result and enables utilisation of the sensor for detection of low pollution levels. The sensor is improved in the sense of a new readout procedure which enables continuous monitoring of the mercury vapor concentration. Previous attempts to solve this problem were based on the deployment of the diffusion filter which is used to form specific gradient of the mercury vapor concentration in front of the sensor surface. In this dissertation it is shown that knowing temporal value of the output voltage and derivative of the output voltage over time is sufficient for the continuous sensor readout. In this way the key problem for the practical application of the sensor is resolved. Milija Sarajlić Microelectronic sensor of elemental mercury Summary Sensor fabrication was improved by introduction of a new manufacturing procedure with a lower number of technology steps which makes fabrication simpler and reduces the cost of the sensor production. All details of the fabrication are thoroughly explained, so based on this guidance it is posssible to reproduce fabrication process by having the appropriate equipment. A survey of the methods and sensors for mercury vapor detection is given in this dissertation. A special attention is given to the sensors based on surface adsorption process. This is due to the fact that the sensor developed within the course of this work operates on the same principle. General data about physical and chemical properties of the mercury are given along with the influence of mercury as a pollutant to the human environment. A special attention is given to the legislative regulations considering working environment protection and human health. It is possible to simplify the fabrication of the sensor and to use to this purpose the equipment already available for the production of microelectronic components with smallest features of 20 μm. The sensor has high sensitivity so that it can register low level pollutions, much lower than the maximum exposure levels set by the legislations. With the new procedure of continuous monitoring proposed in this dissertation the sensor can be used for real-time detection of mercury vapor concentation in air

Surface plasmon - Polariton assisted metal-dielectric multilayers as passband filters for ultraviolet range

We designed and fabricated metal-dielectric multilayers intended for passband filters in the ultraviolet range. We determined the dispersion characteristics by the Bloch approach to evanescent wave resonant coupling and calculated the spectral characteristics using the transfer matrix method while taking into account real dispersion and absorptive losses. We considered the influence of nanoscale interface roughness as a means to couple evanescent electromagnetic field to the propagating far field modes. In our structures both propagating and evanescent modes contribute to the overall performance, resulting in an enhanced transmission in the desired range, while retaining a strong suppression of undesired frequencies of more than four orders of magnitude. In our experiments we used radiofrequent sputtering of silver and silica and characterized our multilayers by UV-vis spectroscopy

Micromechanical properties of composite systems obtained with electrodeposition of thin Ni and Cu films on different substrates

Tanki filmovi Ni i Cu sitnozrne strukture su elektrohemijski istaloženi iz laboratorijski napravljenih sulfamatnih i sulfatnih elektrolita, respektivno. DC elektrohemijsko taloženje filmova Ni je izvedeno na monokristalnim Si pločicama orijentacija (100) i (111), dok je elektrohemijsko taloženje Cu filmova izvedeno na debelim elektrohemijski istaloženim filmovima Ni kao supstratima. U cilju ispitivanja uticaja mikrostrukture supstrata i tankih filmova Ni i Cu na mehanička svojstva ovih kompozitnih struktura, izvršeno je merenje Vikersove mikrotvrdoće sa različitim opterećenjima. Za svaki kompozitni sistem koji se sastoji od tankog filma na supstratu, postoji kritična dubina utiskivanja, kada izmerena tvrdoća ne predstavlja tvrdoću istaloženog filma, već takozvanu “kompozitnu tvrdoću”, zbog učešća supstrata koji doprinosi otporu plastičnoj deformaciji. Odabran je kompozitni model Šiko-Lezaža (C-L model), koji je primenjen na eksperimentalne rezultate u cilju određivanja apsolutne tvrdoće Ni i Cu filmova. Za pomenute kompozitne sisteme je izvršena analiza parametra deformacionog ojačavanja (t/d)m, kojim se može izraziti razlika u odgovoru kompozinih sistema na opterećenja.Thin Ni and Cu films with fine-grained structures have been electrodeposited from self-made sulphamate-based and sulphate-based electrolytes, respectively. DC electrodeposition of Ni films was performed on single crystal Si wafers with different orientations named (100) and (111), and electrodeposition of Cu films was performed on thick electrodeposited Ni films as the substrates. In order to investigate the influence of the microstructure of the substrates and of the Ni and Cu thin films on mechanical properties of these composite structures, Vickers microhardness testings for different loads was done. For any composite system of thin film on a substrate, there is a critical indentation depth, when a measured hardness value is not the hardness of the electrodeposited film, but the so-called “composite hardness”, because the substrate also participates in the plastic deformations. Composite hardness model of Chicot-Lesage was chosen and applied to the experimental data in oreder to determine the absolute film hardness. Analysis of work hardening parameter (t/d)m, that can express the difference in tendency of the composite hardness with the indentation load, was performed for the above-mentioned composite systems

Direct Conversion Of Ionizing Radiation Into Electrical Energy Using PIN Diodes

The energy that comes from the source of ionizing radiation is enormous and quite unused. Using energy from ionizing radiation is a novel concept, while so far in the literature (to the best of our knowledge), only beta radiation has been treated as a possible source of energy (Quenon 2021). This paper focuses on utilizing gamma radiation energy using the Cobalt-60 radiation source. Direct conversion of radiation into electrical energy is possible using pn or pin junction-based semiconductor structures. When high-energy photons hit a semiconductor structure, a built-in electric field of pn junction can separate the generated electron-hole pairs before they recombine, creating the potential difference at the component electrodes. The PIN diodes used in this paper were made in planar technology, with three different active area surfaces: 0.8, 5 and 80 mm2 , at the Center of Microelectronic Technologies, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Serbia. The experiment was conducted in controlled laboratory conditions at the Department of Radiation and Environmental Protection at the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. The range of gamma radiation dose rates for which the PIN diodes have been tested is from 1 µGy/h to 10 Gy/h under controlled conditions at room temperature. It is necessary for the diode to operate in a photovoltaic mode to act as a current source in an electrical circuit. Therefore, during irradiation, the characteristics of diodes: short-circuit current and open-circuit voltage were measured as the most important parameters of the current source. The lowest detected dose rate value of the PIN diode with the largest active area (80 mm2 ) was 5 mGy/h, while diodes with middle (5 mm2 ) and the smallest active area (0.8 mm2 ) were 100 mGy/h. The short-circuit current values of PIN diodes for all active area dimensions have a linear dependence with a given dose rate range. By calculating the short-circuit current density, we obtain that diodes with different active areas have almost the same dependence on the dose rate. This result indicates that the current generated under the ionizing radiation directly depends on the size of the active region of the PIN diode. On the other hand, open-circuit voltage values do not have a linear dependence on the dose rate, even the diode with the smallest active area (0.8 mm2 ) has higher values than the diode with the middle active area (5 mm2 ). For the highest dose rate (10 Gy/h), the short-circuit current value of the PIN diode with the largest active area is 37 nA, and the open-circuit voltage is 118 mV, which can enable power supply of the low power electric circuits by connecting diodes in series and parallel. The research should continue in order to develop a self-powered circuit that will monitor radioactive sources and their environment.XI Conference of the Balkan Physical Union : BPU11; Aug 28 - Sep 1, 2022; BelgradeS12-PSSAP-20

Photon management in semiconductor infrared photodetectors: diffractive and plasmonic antireflective structures

Due to their high specific detectivities and large response speeds, photodetectors based on narrow-bandgap semiconductors like indium-antimonide and mercury cadmium telluride are indispensable for mid- and far-infrared wavelength ranges. Their response is directly proportional to the infrared radiation flux introduced to the detector active area. Thus various photon management techniques are of crucial importance for enhancing their performance. This work analyzes the use of subwavelength nanophotonic structures with antireflective properties. It considers surface-based diffractive optical structure that can be produced by micromachining and nanofabrication. The first part of the consideration is dedicated to all-dielectric subwavelength arrays with 1D and 2D periodicity, which effectively behave as impedance-matching structures with graded effective refractive index. The consideration is then expanded to metal-dielectric structures, especially those belonging to the class of the so-called plasmonic ultra-absorbers. Technologies available in Serbia are then investigated technologies for the fabrication of the dielectric and metaldielectric subwavelength antireflective structures for the infrared, including isotropic and anisotropic etching of surface reliefs and ultrathin-film deposition techniques. It is concluded that diffractive dielectric and plasmonic structures offer a novel degree of freedom in optimization of infrared semiconductor photodetectors

Nanofabrikacija planarnih split ring rezonatora za metamaterijale sa negativnim indeksom prelamanja u infracrvenom opsegu

Experimental nanofabrication of planar structures for one-dimensional metamaterials designed to achieve a negative effective refractive index in the mid-infrared range (5-10 micrometers) was performed. Double split ring and complementary double split ring resonators (SRR and CSRR) with square and circular geometries, were chosen to be fabricated since these are the basic building blocks to achieve a negative effective dielectric permittivity and magnetic permeability. Scanning probe nanolithography with z-scanner movement was used to fabricate straight-line and curvilinear segments with a line width of 80-120 nm. The geometries were delineated in 20 nm thin silver layers sputter-deposited on a positive photoresist substrate spin-coated on polished single crystal silicon wafers, as well as on polycarbonate slabs. The morphology of the structures was characterized by atomic force microscopy. The feature repeatibility was 60-150 nm, depending on the process conditions and the feature complexity. The nanolithographic groove depth in different samples ranged from 4 nm to 80 nm.Vršena je eksperimentalna nanofabrikacija planarnih struktura za jednodimenzionalne metamaterijale projektovane da dostignu negativnu vrednost efektivnog indeksa prelamanja u srednjetalasnom infracrvenom opsegu (5-10 mikrometara). Napravljeni su dvostruki split ring i komplementarni split ring rezonatori (SRR i CSRR) sa kvadratnom i kružnom geometrijom, pošto se oni mogu koristiti kao osnovni gradivni blokovi za dostizanje negativne efektivne dielektrične permitivnosti i magnetske permeabilnosti. Korišćena je nanolitografija skanirajućom sondom u režimu z-pomeraja skanera da bi se napravili pravolinijski i zakrivljeni segmenti sa širinom linije 80 - 120 nm. Geometrija je delineirana u 20 nm debelim slojevima srebra deponovanim spaterovanjem na podlogu od fotorezista nanetu spinerom na polirane pločice monokristala silicijuma, kao i na polikarbonatnim pločicama. Morfologija struktura karakterisana je "atomic force" mikroskopom. Ponovljivost detalja bila je 60-150 nm, zavisno od procesnih uslova i složenosti detalja. Dubina nanolitografskih brazdi menjanja je u opsegu od 4 do 80 nm

Recharging process of commercial floating-gate MOS transistor in dosimetry application

We investigated the recharging process of commercial floating gate device (EPAD) during the six different dose rates and ten irradiation cycles with the highest dose rate. Dose rate dependence of the floating gate dosimeter was observed from 1 Gy/h to 26 Gy/h (H2O). There is no change of the dosimetric characteristic with a constant dose rate of 26 Gy/h for ten cycles. The absorbed dose does not affect the drift of the threshold voltage readings after the irradiation steps. The reprogramming characteristic is not degrading with the absorbed dose for the ten irradiation cycles, giving the promising potential in the application for dosimetric purposes

Nanoaperture array-based plasmonic sensors of dangerous substances using transparent conductive oxides

Detection of dangerous substances like explosives, pathogenic microorganisms and toxic chemical is of utmost interest for homeland defense and anti-terrorist actions. Among the devices of choice for that purpose are surface plasmon resonance (SPR) chemical-biological sensors since they are ultra-fast, highly sensitive and label-free. We consider one of the advanced types of SPR sensors, those with ordered arrays of subwavelength apertures in plasmonic material. Such sensors show high sensitivity in transmission readout mode, are useful for both liquid and gaseous analytes and can be used as a building block for complex microfluidic systems for multianalyte detection. Simultaneously, high electromagnetic field concentrations in nanoapertures enhance nonlinear effects, thus further facilitating detection of complex molecules of dangerous substances. We performed finite element simulation of the performance of such devices for various materials and nanoaperture sizes and shapes. We dedicated special attention to the case when the subwavelength array is formed in transparent conductive oxide (TCO) host. An example of TCO is tin oxide, routinely used in thin layers for window defrosting and defogging elements in armored vehicles. We show that compared to conventional nanoaperture array sensors based on metal hosts the TCO-based devices simultaneously offer enhanced selectivity and retain high sensitivity

Ultrafast humidity sensor based on liquid phase exfoliated graphene

Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation (LPE) followed by Langmuir-Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.Comment: 18 pages, 13 figure

The concept of portable multifunctional measurement instrument based on ICTM sensors

Several types of MEMS and thin-film based sensors have been developed at the Institute of Chemistry, Technology and Metallurgy (ICTM), including piezoresistive pressure sensors, a multipurpose thermal sensor, and an adsorption-based mercury vapor sensor. In this paper, we present the concept of a portable electronic instrument that can be used with different combinations of pressure, thermal and/or mercury sensors. Such an instrument is highly configurable, thus enabling various measurements to be performed in different applications, from industrial plants to environmental monitoring. Since the mentioned sensors have different requirements in terms of sensor excitation, as well as different ranges of their output signals, the design of the instrument is a demanding task. Additional design requirements are related to the portability of the instrument, including the overall dimensions, power source and consumption, and communication methods. One of the possible directions of further development is the design of a rugged version of the instrument, intended for harsh environments