Structural and Electrical Characterization of Pure and Al-Doped ZnO Nanorods

Pure and Al-doped (3 at.%) ZnO nanorods were prepared by two-step synthesis. In the first step, ZnO thin films were deposited on silicon wafers by spin coating ; then, ZnO nanorods (NR) and Al- doped ZnO NR were grown using a chemical bath method. The structural properties of zincite nanorods were determined by X-ray diffraction (XRD) and corroborated well with the morphologic properties obtained by field-emission gun scanning electron microscopy (FEG SEM) with energy- dispersive X-ray spectroscopy (EDS). Morphology results revealed a minute change in the nanorod geometry upon doping, which was also visible by Kelvin probe force microscopy (KPFM). KPFM also showed preliminary electrical properties. Detailed electrical characterization of pure and Al-doped ZnO NR was conducted by temperature-dependent current–voltage (I–V) measurements on Au/(Al)ZnO NR/n-Si junctions. It was shown that Al doping increases the conductivity of ZnO NR by an order of magnitude. The I–V characteristics of pure and Al-doped ZnO NR followed the ohmic regime for lower voltages, whereas, for the higher voltages, significant changes in electric conduction mechanisms were detected and ascribed to Al- doping. In conclusion, for future applications, one should consider the possible influence of the geometry change of (Al)ZnO NRs on their overall electric transport properties

Showcase of tools for preparing, modifying and describing thin lms for energy conversion devices with special attention on plasma phenomenology

This paper draws attention to the wide range of capacities of the roup, including chemical and physical deposition, modification and processing techniues, and advanced characterisations. In particular, this work demystifies the new plasma discharge method for the synthesis of thin films, which is still under development. Specifically, the coupled spark plasma ablation deposition (SPAD) can be performed at almost ambient conditions in various configurations with respect to several deposition reactors, proving powerful, versatile, green, and easy-to-use nature of the method. Composition-wise, up to 4 element material can be derived combining pure electrodes, however the derived composition can be broader when using alloy electrodes. It is indisputable that SPAD is capable of producing thin films at a significantly reduced cost compared to other methods.which we want to put in use for the constituent layers of the last generation of energy conversion devices. enerally, the SPAD optimisation envelope heavily differs for the case of intended products nanoparticle vs thin film, or metal vs metal oxide, or crystalline vs amorphous. Here, we will provide a more detailed description of the ablation parameters that are necessary to achieve the various crystallinities of nanomaterials. Copper nanoparticles and thin films were derived via SPAD and additionally thermally treated. (Micro)structural and thermal evolution points out to interesting development of the surface morphologies. In addition, the results enabled the correlation between oxygen plasma concentration and order of crystallinity in the thin films

Humidity sensing ceria thin-films

Lowering the constitutive domains of semiconducting oxides to the nano-range has recently opened up the possibility of added benefit in the research area of sensing materials, in terms both of greater specific surface area and pore volume. Among such nanomaterials, ceria has attracted much attention ; therefore, we chemically derived homogeneous ceria nanoparticle slurries. One set of samples was tape-casted onto a conducting glass substrate to form thin-films of various thicknesses, thereby avoiding demanding reaction conditions typical of physical depositions, while the other was pressed into pellets. Structural and microstructural features, along with electrical properties and derivative humidity-sensing performance of ceria thin-films and powders pressed into pellets, were studied in detail. Particular attention was given to solid- state impedance spectroscopy (SS-IS), under controlled relative humidity (RH) from 30%– 85%, in a wide temperature and frequency range. Moreover, for the thin-film setup, measurements were performed in surface-mode and cross-section- mode. From the results, we extrapolated the influence of composition on relative humidity, the role of configuration and thin-film thickness on electrical properties, and derivative humidity- sensing performance. The structural analysis and depth profiling both point to monophasic crystalline ceria. Microstructure analysis reveals slightly agglomerated spherical particles and thin-films with low surface roughness. Under controlled humidity, the shape of the conductivity spectrum stays the same along with an increase in RH, and a notable shift to higher conductivity values. The relaxation is slow, as the thickness of the pellet slows the return of conductivity values. The increase in humidity has a positive effect on the overall DC conductivity, similar to the temperature effect for semiconducting behavior. As for the surface measurement setup, the thin-film thickness impacts the shape of the spectra and electrical processes. The surface measurement setup turns out to be more sensitive to relative humidity changes, emphasized with higher RH, along with an increase in thin-film thickness. The moisture directly affects the conductivity spectra in the dispersion part, i.e., on the localized short-range charge carriers. Moisture sensitivity is a reversible process for thin-film samples, in contrast to pellet form samples

Development of nano-structured ZnO/TiO2 thin films for photovoltaic and photocatalytic applications

U ovoj disertaciji istraživani su tanki filmovi ZnO, TiO2 te kompozita ZnO@TiO2. Cilj je bio pripraviti nanostrukturirane materijale pogodne za fotokatalitičke i fotonaponske primjene. Za provjeru uspješnost postizanja željenih svojstava navedenih mikrostrukturiranih i nanostrukturiranih materijala od ključne važnosti je određivanje morfoloških i strukturnih svojstava, što se postiglo korištenjem prvenstveno elektronske mikroskopije i Ramanove spektroskopije. Za potrebe priprave fotonaponskih ćelija u čvrstom stanju s nanostrukturiranim ZnO tankim filmovima kao slojevima za prijenos elektrona bilo je potrebno optimirati debljinu i sastav susjednih slojeva što je utjecalo na pojavu električne histereze u različitim razmjerima. Nanostrukturirani TiO2 filmovi dodatno su dekorirani sa česticama i spojevima baziranim na Ag ili Cu za potrebe primjene u fotokatalitičkim reaktorima. Tim procesom je poboljšana efikasnost razgradnje organskih onečišćivala. Ispitana je mogućnost priprave filmova kompozitnih ZnO@TiO2 nanostruktura korištenjem niza fizikalnih i kemijskih metoda nanošenja TiO2 na nanostrukture ZnO. Utvrđena je najveća uspješnost nanošenja kemijskim metodama, što je razvidno iz najvećih vrijednosti postignutih vodljivosti i transmisije filmova. Problematika razjašnjavanja određenih mikrostrukturnih specifičnosti kompozita ZnO@TiO2 ostaje izazov s ciljem daljnjeg poboljšavanje efikasnosti i stabilnosti fotonaponskih i fotokatalitičkih sustava.This dissertation investigates ZnO, TiO2 and ZnO@TiO2 composites thin films. The aim was to prepare nanostructured materials suitable for photocatalytic and photovoltaic applications. In order to validate the obtaining of microstructured and nanostructured materials with desired properties, it was necessary to optimise morphologic and structural properties, which was primarily achieved using electron microscopy and Raman spectroscopy. In order to prepare solid state solar cells with nanostructured ZnO thin films for transport of the charge carriers, it was necessary to optimise the thickness and the composition of the adjacent layers, which influenced the extent of the occurring electric hysteresis. For use in photocatalytic reactors, TiO2 nanostructures were additionally decorated with Ag particles or Cu compounds, which improved the decomposition rate and efficiency of organic pollutants. A possibility of preparing ZnO@TiO2 thin film composites using various physical and chemical methods of TiO2 layer deposition on ZnO nanostructures was investigated. Chemical methods rose above others since composite films obtained thereof displayed the highest conductivity and the highest transmission properties. The challenges related with clarifying microstructural particularities of the ZnO@TiO2 composites remain with the aim of further improvement of efficiency and stability of photovoltaic and photocatalytic systems

Cyberbullying and social media

Internet je svjetska komunikacijska mreža. To je javno dostupna, globalna, paketna, podatkovna mreža koja povezuje računala i računalne mreže korištenjem istoimenog protokola. Društvena mreža je vrsta Internetskog servisa koji služi za međusobno povezivanje korisnika društvenih mreža. ISP (Internet service provider) tvrtke korisnicima pružaju usluge spajanja na Internet. U Hrvatskoj postoje komercijalne i akademske ISP tvrtke. Postoji niz raznih vrsta društvenih mreža. Neke od najpopularnijih su chat sobe, forumi, blogovi i elektronička pošta. Najviše zlostavljanja preko Interneta ipak se odnosi na popularne mreže današnjice kao što su Facebook, Instagram i Youtube. Elektroničko nasilje je svaka zlonamjerna i ponavljana uporaba informacijskih i komunikacijskih tehnologija kako bi se nekome nanijela šteta. Elektroničko nasilje uključuje poticanje grupne mržnje, napade na privatnost, uznemiravanje, uhođenje, vrijeđanje, nesavjestan pristup štetnim sadržajima, širenje nasilja i uvredljive komentare. Nasilnici žele osjećati kontrolu i moć nad drugima te im zbog toga nedostaje suosjećanja za žrtve. Nasilnici su vrlo često i sami bili žrtve fizičkog zlostavljanja i nasilništva. Žrtve nasilništva većinom su slabije od nasilnika. One su ekonomski, fizički, rastom ili spolom slabiji i zbog toga podložniji napadima. Uglavnom nemaju mogućnosti da pruže otpor. Najčešće su žrtve početnici na Internetu te ljudi koji su neiskusni u pitanjima mrežnog bontona. Nasilničko ponašanje može izazvati brojne posljedice kao što su usamljenost, depresivnost, tugu, uplašenost, nesigurnost, nisko samopouzdanje pa i bolest, što ostaje prisutno dalje kroz život. Internet je globalan i teško mu je nametnuti pravni okvir te su mnogi ljudi uvjereni da Internetom vlada potpuno bezakonje no to ipak nije istina.Internet is a global communications network. It is a publicly accessible global packet data network that connects computers and computer networks using the protocol of the same name. A social network is a type of Internet service that is used to interconnect users of social networks. ISP (Internet service provider) company provides connection services to the Internet. In Croatia there are commercial and academic ISP companies. There are a number of different types of social networks. Some of the most popular are chat rooms, forums, blogs and email. Most of abuse over the Internet still applies to today's popular network such as Facebook, Instagram and Youtube. Cyberbullying is malicious and repeated use of information and communication technologies to inflict damage to someone. Cyberbullying involves encouraging group hatred, attacks on privacy, harassment, stalking, abuse, malpractice access to harmful content, spreading violence and offensive comments. Bullies want to feel control and power over others and they therefore lack of sympathy for the victims. Bullies are often themselves been victims of physical abuse and bullying. Victims of bullying are mostly weaker than bullies. They are economically or physically weaker, smaller by growth or weaker sex, and therefore vulnerable to attack, mostly not able to resist. The most common victims are beginners on the Internet and people who are inexperienced in matters of network etiquette. Bullying can cause numerous consequences such as loneliness, depression, sadness, fearfulness, insecurity, low self-esteem and even disease, which is retained on through life. Internet is global and it is difficult to impose a legal framework and many people are convinced that Internet is related with complete lawlessness but that is not true

Development of nano-structured ZnO/TiO2 thin films for photovoltaic and photocatalytic applications

U ovoj disertaciji istraživani su tanki filmovi ZnO, TiO2 te kompozita ZnO@TiO2. Cilj je bio pripraviti nanostrukturirane materijale pogodne za fotokatalitičke i fotonaponske primjene. Za provjeru uspješnost postizanja željenih svojstava navedenih mikrostrukturiranih i nanostrukturiranih materijala od ključne važnosti je određivanje morfoloških i strukturnih svojstava, što se postiglo korištenjem prvenstveno elektronske mikroskopije i Ramanove spektroskopije. Za potrebe priprave fotonaponskih ćelija u čvrstom stanju s nanostrukturiranim ZnO tankim filmovima kao slojevima za prijenos elektrona bilo je potrebno optimirati debljinu i sastav susjednih slojeva što je utjecalo na pojavu električne histereze u različitim razmjerima. Nanostrukturirani TiO2 filmovi dodatno su dekorirani sa česticama i spojevima baziranim na Ag ili Cu za potrebe primjene u fotokatalitičkim reaktorima. Tim procesom je poboljšana efikasnost razgradnje organskih onečišćivala. Ispitana je mogućnost priprave filmova kompozitnih ZnO@TiO2 nanostruktura korištenjem niza fizikalnih i kemijskih metoda nanošenja TiO2 na nanostrukture ZnO. Utvrđena je najveća uspješnost nanošenja kemijskim metodama, što je razvidno iz najvećih vrijednosti postignutih vodljivosti i transmisije filmova. Problematika razjašnjavanja određenih mikrostrukturnih specifičnosti kompozita ZnO@TiO2 ostaje izazov s ciljem daljnjeg poboljšavanje efikasnosti i stabilnosti fotonaponskih i fotokatalitičkih sustava.This dissertation investigates ZnO, TiO2 and ZnO@TiO2 composites thin films. The aim was to prepare nanostructured materials suitable for photocatalytic and photovoltaic applications. In order to validate the obtaining of microstructured and nanostructured materials with desired properties, it was necessary to optimise morphologic and structural properties, which was primarily achieved using electron microscopy and Raman spectroscopy. In order to prepare solid state solar cells with nanostructured ZnO thin films for transport of the charge carriers, it was necessary to optimise the thickness and the composition of the adjacent layers, which influenced the extent of the occurring electric hysteresis. For use in photocatalytic reactors, TiO2 nanostructures were additionally decorated with Ag particles or Cu compounds, which improved the decomposition rate and efficiency of organic pollutants. A possibility of preparing ZnO@TiO2 thin film composites using various physical and chemical methods of TiO2 layer deposition on ZnO nanostructures was investigated. Chemical methods rose above others since composite films obtained thereof displayed the highest conductivity and the highest transmission properties. The challenges related with clarifying microstructural particularities of the ZnO@TiO2 composites remain with the aim of further improvement of efficiency and stability of photovoltaic and photocatalytic systems

Development of nano-structured ZnO/TiO2 thin films for photovoltaic and photocatalytic applications

U ovoj disertaciji istraživani su tanki filmovi ZnO, TiO2 te kompozita ZnO@TiO2. Cilj je bio pripraviti nanostrukturirane materijale pogodne za fotokatalitičke i fotonaponske primjene. Za provjeru uspješnost postizanja željenih svojstava navedenih mikrostrukturiranih i nanostrukturiranih materijala od ključne važnosti je određivanje morfoloških i strukturnih svojstava, što se postiglo korištenjem prvenstveno elektronske mikroskopije i Ramanove spektroskopije. Za potrebe priprave fotonaponskih ćelija u čvrstom stanju s nanostrukturiranim ZnO tankim filmovima kao slojevima za prijenos elektrona bilo je potrebno optimirati debljinu i sastav susjednih slojeva što je utjecalo na pojavu električne histereze u različitim razmjerima. Nanostrukturirani TiO2 filmovi dodatno su dekorirani sa česticama i spojevima baziranim na Ag ili Cu za potrebe primjene u fotokatalitičkim reaktorima. Tim procesom je poboljšana efikasnost razgradnje organskih onečišćivala. Ispitana je mogućnost priprave filmova kompozitnih ZnO@TiO2 nanostruktura korištenjem niza fizikalnih i kemijskih metoda nanošenja TiO2 na nanostrukture ZnO. Utvrđena je najveća uspješnost nanošenja kemijskim metodama, što je razvidno iz najvećih vrijednosti postignutih vodljivosti i transmisije filmova. Problematika razjašnjavanja određenih mikrostrukturnih specifičnosti kompozita ZnO@TiO2 ostaje izazov s ciljem daljnjeg poboljšavanje efikasnosti i stabilnosti fotonaponskih i fotokatalitičkih sustava.This dissertation investigates ZnO, TiO2 and ZnO@TiO2 composites thin films. The aim was to prepare nanostructured materials suitable for photocatalytic and photovoltaic applications. In order to validate the obtaining of microstructured and nanostructured materials with desired properties, it was necessary to optimise morphologic and structural properties, which was primarily achieved using electron microscopy and Raman spectroscopy. In order to prepare solid state solar cells with nanostructured ZnO thin films for transport of the charge carriers, it was necessary to optimise the thickness and the composition of the adjacent layers, which influenced the extent of the occurring electric hysteresis. For use in photocatalytic reactors, TiO2 nanostructures were additionally decorated with Ag particles or Cu compounds, which improved the decomposition rate and efficiency of organic pollutants. A possibility of preparing ZnO@TiO2 thin film composites using various physical and chemical methods of TiO2 layer deposition on ZnO nanostructures was investigated. Chemical methods rose above others since composite films obtained thereof displayed the highest conductivity and the highest transmission properties. The challenges related with clarifying microstructural particularities of the ZnO@TiO2 composites remain with the aim of further improvement of efficiency and stability of photovoltaic and photocatalytic systems