1
|
Silva JPB, Wang J, Koster G, Rijnders G, Negrea RF, Ghica C, Sekhar KC, Moreira JA, Gomes MJM. Hysteretic Characteristics of Pulsed Laser Deposited 0.5Ba(Zr 0.2Ti 0.8)O 3-0.5(Ba 0.7Ca 0.3)TiO 3/ZnO Bilayers. ACS Appl Mater Interfaces 2018; 10:15240-15249. [PMID: 29630331 DOI: 10.1021/acsami.8b01695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the present work, we study the hysteretic behavior in the electric-field-dependent capacitance and the current characteristics of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT)/ZnO bilayers deposited on 0.7 wt % Nb-doped (001)-SrTiO3 (Nb:STO) substrates in a metal-ferroelectric-semiconductor (MFS) configuration. The X-ray diffraction measurements show that the BCZT and ZnO layers are highly oriented along the c-axis and have a single perovskite and wurtzite phases, respectively, whereas high-resolution transmission electron microscopy revealed very sharp Nb:STO/BCZT/ZnO interfaces. The capacitance-electric field ( C- E) characteristics of the bilayers exhibit a memory window of 47 kV/cm and a capacitance decrease of 22%, at a negative bias. The later result is explained by the formation of a depletion region in the ZnO layer. Moreover, an unusual resistive switching (RS) behavior is observed in the BCZT films, where the RS ratio can be 500 times enhanced in the BCZT/ZnO bilayers. The RS enhancement can be understood by the barrier potential profile modulation at the depletion region, in the BCZT/ZnO junction, via ferroelectric polarization switching of the BCZT layer. This work builds a bridge between the hysteretic behavior observed either in the C- E and current-electric field characteristics on a MFS structure.
Collapse
Affiliation(s)
- J P B Silva
- Centre of Physics , University of Minho , Campus de Gualtar , 4710-057 Braga , Portugal
- IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia , Faculdade de Ciências da Universidade do Porto , Rua do Campo Alegre 687 , 4169-007 Porto , Portugal
| | - J Wang
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, Inorganic Materials Science , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
| | - G Koster
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, Inorganic Materials Science , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
| | - G Rijnders
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, Inorganic Materials Science , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
| | - R F Negrea
- National Institute of Materials Physics , 405A Atomistilor , 077125 Magurele , Romania
| | - C Ghica
- National Institute of Materials Physics , 405A Atomistilor , 077125 Magurele , Romania
| | - K C Sekhar
- Department of Physics, School of Basic and Applied Sciences , Central University of Tamil Nadu , 610101 Thiruvarur , India
| | - J Agostinho Moreira
- IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia , Faculdade de Ciências da Universidade do Porto , Rua do Campo Alegre 687 , 4169-007 Porto , Portugal
| | - M J M Gomes
- Centre of Physics , University of Minho , Campus de Gualtar , 4710-057 Braga , Portugal
| |
Collapse
|
2
|
Mihaiescu DE, Cristescu R, Dorcioman G, Popescu CE, Nita C, Socol G, Mihailescu IN, Grumezescu AM, Tamas D, Enculescu M, Negrea RF, Ghica C, Chifiriuc C, Bleotu C, Chrisey DB. Functionalized magnetite silica thin films fabricated by MAPLE with antibiofilm properties. Biofabrication 2012; 5:015007. [PMID: 23254399 DOI: 10.1088/1758-5082/5/1/015007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We report on the fabrication of magnetite/salicylic acid/silica shell/antibiotics (Fe(3)O(4)/SA/SiO(2)/ATB) thin films by matrix-assisted pulsed laser evaporation (MAPLE) to inert substrates. Fe(3)O(4)-based powder have been synthesized and investigated by XRD and TEM. All thin films were studied by FTIR, SEM and in vitro biological assays using Staphylococcus aureus and Pseudomonas aeruginosa reference strains, as well as eukaryotic HEp-2 cells. The influence of the obtained nanosystems on the microbial biofilm development as well as their biocompatibility has been assessed. For optimum deposition conditions, we obtained uniform adherent films with the composition identical with the raw materials. Fe(3)O(4)/SA/SiO(2)/ATB thin films had an inhibitory activity on the ability of microbial strains to initiate and develop mature biofilms, in a strain- and antibiotic-dependent manner. These magnetite silica thin films are promising candidates for the development of novel materials designed for the inhibition of medical biofilms formed by different pathogenic agents on common substrates, frequently implicated in the etiology of chronic and hard to treat infections.
Collapse
Affiliation(s)
- D E Mihaiescu
- Faculty of Applied Chemistry and Materials Science, Politehnica University of Bucharest, 1-7 Polizu Street, Bucharest, Romania
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Sandu V, Nicolescu MS, Kuncser V, Popa S, Pasuk I, Ghica C, Sandu E. Structure and magnetic properties of nanosized magnetite obtained by glass recrystallization. J Nanosci Nanotechnol 2012; 12:5043-5050. [PMID: 22905574 DOI: 10.1166/jnn.2012.4943] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present the preparation, structural and magnetic properties of nanosized magnetite obtained by the crystallization of a series of Fe-containing borosilicate glasses. Several compositions with the ratio Fe2O3/SiO2 spanning from 0.37 to 0.67 were investigated as a function of two nucleators Cr2O3 and P2O5, respectively, and modifiers and intermediates (Al2O3 and MgO). Mössbauer spectroscopy revealed the degree, the type and the location of disorder induced by a specific composition and nucleators. In addition to magnetite, it was also revealed the presence of large amounts of Fe-rich paramagnetic phases. The magnetic response is analysed in relation with the amount of Fe ions which remain dispersed in the glassy matrix as noninteracting (paramagnetic) ions. We discuss the role of the nucleators on the disorder in both tetrahedral and octahedral sites of the magnetite.
Collapse
Affiliation(s)
- V Sandu
- National Institute of Materials Physics-Bucharest, Magurele, Ilfov, 077125, Romania
| | | | | | | | | | | | | |
Collapse
|
4
|
Tudose M, Culita D, Marinescu G, Ghica C, Ionita P. Chemically Modified (Nano)Silica as Sensitive Material for Arginine and Lysine. J Inorg Organomet Polym Mater 2011. [DOI: 10.1007/s10904-011-9470-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
5
|
Tudosa R, Vartej P, Horhoianu I, Ghica C, Mateescu S, Dumitrache I. Maternal and fetal complications of the hypothyroidism-related pregnancy. Maedica (Bucur) 2010; 5:116-23. [PMID: 21977134 PMCID: PMC3150006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Thyroid pathology worsens during pregnancy. Hypothyroidism can be pre-existent or may begin during pregnancy period. Most of the patients who presented hypothyroidism during pregnancy have a history of thyroid disease for which they have undergone treatment (medical, surgical or radioisotopes). Hypothyroidism is difficult to be diagnosed during pregnancy as the signs can belong to pregnancy itself. Changes in thyroid function have a major negative impact on both mother and fetus.Complications that arise depend on the severity of hypothyroidism, on how appropriately and early the treatment will be initiated, on other obstetrical and extragenital pathologies associated with the present pregnancy. Clinical symptoms are polymorphic, often nonspecific, and are related mainly to the time of occurrence and to the severity of thyroid hormone deficiency. The appropriate, early administered treatment and maintenance of a normal level of thyroid hormones minimize the risk of maternal and fetal complications and make it possible that the pregnancy may be carried to term without severe complications.
Collapse
Affiliation(s)
- Rodica Tudosa
- "Carol Davila" University of Medicine and Farmacy, Obstetrics-Gynaecology Clinic, Emergency University Hospital, Bucharest, Romania
| | - P Vartej
- "Carol Davila" University of Medicine and Farmacy, Obstetrics-Gynaecology Clinic, Emergency University Hospital, Bucharest, Romania
| | - Irina Horhoianu
- "Carol Davila" University of Medicine and Farmacy, Obstetrics-Gynaecology Clinic, Emergency University Hospital, Bucharest, Romania
| | - C. Ghica
- Obstetrics-Gynaecology Department, Curtea de Arges Hospital, Romania
| | - Stela Mateescu
- Obstetrics-Gynaecology Department, Campulung Muscel Maternity Hospital, Romania
| | - I Dumitrache
- Obstetrics-Gynaecology Department, Curtea de Arges Maternity Hospital, Romania
| |
Collapse
|
6
|
Ghica C, Ion L, Epurescu G, Nistor L, Antohe S, Dinescu M. Organic photovoltaic cells based on ZnO thin film electrodes. J Nanosci Nanotechnol 2010; 10:1322-1326. [PMID: 20352794 DOI: 10.1166/jnn.2010.1836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Due to its wide band-gap (ca. 3.4 eV), ZnO is a possible candidate material to be used as transparent electrode for a new class of photovoltaic (PV) cells. Also, an increased interest for the photovoltaic properties of several organic monomers and polymers (merocyanines, phthalocyanines and porphyrins) was noticed, because of their high optical absorption in the visible region of the spectrum allowing them to be used as potential inexpensive materials for solar cells. Preparation and properties of CuPc (copper phthalocyanine) based photovoltaic cells using ZnO thin films as transparent conductor electrodes are presented in this paper. ZnO layers are grown by pulsed laser deposition, while the organic layers are obtained by thermal evaporation. Structural characterization is performed by electron microscopy. Optical and transport properties of the mutilayered structures are obtained by electrical and spectro-photometric measurements. The influence of the ZnO-polymer interface on the external quantum efficiency (EQE) of the photovoltaic cell is clearly evidenced by our measurements.
Collapse
Affiliation(s)
- C Ghica
- National Institute of Materials Physics, Magurele 077125, Romania
| | | | | | | | | | | |
Collapse
|
7
|
Nelea V, Pelletier H, Iliescu M, Werckmann J, Craciun V, Mihailescu IN, Ristoscu C, Ghica C. Calcium phosphate thin film processing by pulsed laser deposition and in situ assisted ultraviolet pulsed laser deposition. J Mater Sci Mater Med 2002; 13:1167-1173. [PMID: 15348661 DOI: 10.1023/a:1021150207350] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Calcium orthophosphates (CaP) and hydroxyapatite (HA) were intensively studied in order to design and develop a new generation of bioactive and osteoconductive bone prostheses. The main drawback now in the CaP and HA thin films processing persists in their poor mechanical characteristics, namely hardness, tensile and cohesive strength, and adherence to the metallic substrate. We report here a critical comparison between the microstructure and mechanical properties of HA and CaP thin films grown by two methods. The films were grown by KrF* pulsed laser deposition (PLD) or KrF* pulsed laser deposition assisted by in situ ultraviolet radiation emitted by a low pressure Hg lamp (UV-assisted PLD). The PLD films were deposited at room temperature, in vacuum on Ti-5Al-2.5Fe alloy substrate previously coated with a TiN buffer layer. After deposition the films were annealed in ambient air at 500-600 degrees C. The UV-assisted PLD films were grown in (10(-2)-10(-1) Pa) oxygen directly on Ti-5Al-2.5Fe substrates heated at 500-600 degrees C. The films grown by classical PLD are crystalline and stoichiometric. The films grown by UV-assisted PLD were crystalline and exhibit the best mechanical characteristics with values of hardness and Young modulus of 6-7 and 150-170 GPa, respectively, which are unusually high for the calcium phosphate ceramics. To the difference of PLD films, in the case of UV-assisted PLD, the GIXRD spectra show the decomposition of HA in Ca(2)P(2)O(7), Ca(2)P(2)O(9) and CaO. The UV lamp radiation enhanced the gas reactivity and atoms mobility during processing, increasing the tensile strength of the film, while the HA structure was destroyed.
Collapse
Affiliation(s)
- V Nelea
- Laboratoire d'Ingénierie de Surface, Ecole Nationale Supérieure des Arts et Industries, 24 Bld. de la Victoire, F-67084, Strasbourg, France.
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Daoudi K, Sandu C, Teodorescu V, Ghica C, Canut B, Blanchin M, Roger J, Oueslati M, Bessaïs B. Rapid thermal annealing procedure for densification of sol-gel indium tin oxide thin films. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1463-0184(02)00028-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|