Romnet-Era network

3.4.2.2 Technologies associated with the production, transformation and processing of knowledge-based multifunctional materials

The National Institute of Materials Physics ( NIMP-Bucharest, Romania) came into being in 1977 under the name of Institute for Physics and Technology of Materials. The actual name was given in 1996 after a national accreditation procedure. Nowadays, the NIMP Bucharest is devoted to fundamental and applied research and development, with particular emphasis in the fields of solid state physics and materials research. Among the goals of the NIMP are: the preparation, characterization and study of the physical properties of new materials connected to high technology products and devices; the development of analytical techniques and methods applied in materials science; training of young scientists, PhD and MSc students; supply of both public institutions as well as companies with the Institute’s R&D know-how and expertise in the field of high-tech materials

The involved laboratory has an internationally recognized experience in: photoelectric phenomena in various materials and heterostructures; charge transport and trap investigation in bulk materials and thin films; ferroelectricity and related materials; field effect phenomena; radiation detectors, IR sensors. It possess a well equipped laboratory for complex electric/ferroelectric/photoelectric characterization of materials and structures, as well some facilities for thin film preparation using un-expensive chemical methods.

The large objective of the proposing group is to study in detail the properties of the ferroelectric materials and of the mixed ferroelectric-semiconductor structures (either multi-layers or nanocomposites).

The proposed subject is covering several specific topics that, by themselves, can constitute the research object of a STREP. These are:

Elucidating the role of interface grain boundaries in ferroelectric thin films and their effect on overall electric/ferroelectric properties of a metal-ferroelectric-metal (MFM) structure. It is a general mistake made by many peoples working in the field of ferroelectric thin films to ignore the grain boundaries or the other internal interfaces existing in ceramic films, and to consider them as homogeneous materials with well defined properties. That despite an overwhelming amount of experimental results showing that the properties of the films are very sensitive to the process conditions. Internal interfaces in thin ferroelectric films can introduce field and charge non-homogeneities affecting polarization switching and the leakage currents, as well the dielectric properties bringing extrinsic contributions to the dielectric constant.
Porous ferroelectric materials and nano-composites for electromagnetic radiation detection. The aim is to develop not very expensive technologies for deposition of sufficiently thick, good quality films, to be used for light detection in domains from UV to IR. By mixing the nanoporous ferroelectric material with light sensitive semiconductor nano-crystals it is hoped to obtain nanocomposites with potentially enhanced propeties, or even with radically new properties in the field of optoelectronic.
Ferroelectric, ceramic, thin films with radically new properties in the field of microelectronics. The goal is to obtain materials with high tunnability of the dielectric constant in both low frequency domain as well in the microwave domain. Another goal is to obtain materials with large values of the dielectric constant, useful for small size capacitors.
Complex field effect devices with applications in optoelectronic. This is based on field effect photoconductivity, and includes study of the interface phenomena with and without light in complex heterostructures involving dielectric, ferroelectric, and semiconductor thin films and materials.

Depending on the potential partners interest, the proposal can focus on one of the above objectives.

The National Institute of Materials Physics (NIMP) Bucharest ( Romania) is one of the physics institutes belonging to Institute of Atomic Physics (IFA-Bucharest-Magurele), one major research center in Romania.
The general goal of the NIMP is to conduct high level basic and applied research in some selected areas of Solid State Physics and Materials Science. With a high qualified personnel (14 PhD supervisors, 89 Doctors, 54 PhD students), the NIMP is implied an important number of national and international R &D projects.

Abstract privind rezultatele si potentialul stiintific, tehnic, etc. in cadrul temei propuse in raport cu prevederile capitolelor 3.4.2. si 3.4.3 (max 1 pagina)

The sintering-sublimation technique has been designed to increase the reliability of photoconducting devices mainly by decreasing the donors’ concentration which determines a high sensitivity. This method combines three different processes i.e. vacuum evaporation, thin layers growth from vapors and ceramic pellets sintering. Previous observations has shown that when sintering CdS ceramic pellets, transparent, high purity monocrystals condensed on the cooler parts of the oven. This process becomes more effective if are used pellets containing together with the raw A 2B 6 other component presenting a limited reactivity as nonstoichiometric chromium oxide. This oxide provide surfaces on which thin A 2B 6 layers are crystallizing. At the same time, the nonstoichiometric Cr 2O 3 can react with the oxygen allowing a more efficient control of the properties of the A 2B 6 thin film generated as a result of the above mentioned sublimation-condensing process. The process of film growth as well as the fast firing sintering take place simultaneously in a reductive atmosphere (a mixture of CO, CO 2 and N 2), specific to graphite crucibles, inhibits a further oxidation of A 2B 6 films and thus improves significantly their quality. This new method produce high reliability photo conducting ceramic films A 2B 6 onto a porous ceramic thin film Cr 2O 3 sustained by a Cd 2CrO 3 core, produced by the reaction between the nonstoichiometric Cr 2O 3 and interstitial Cd atoms. The thin ceramic polycrystalline films have been grown by using an installation similar to those used to grow crystals by the Bridgman method. It consists of a crucible made of nuclear graphite fixed on a rod which executes an oscillating movement combined with a slow rotation (10 rpm) along the axis of a vertical oven. The distribution of the temperature along the oven axis is characterized by the presence of two steps corresponding to each extremity. Between these steps, the temperature increase monotonously with a medium gradient equal to 100 K cm -1. As a result of the crucible displacement within the oven, transitory temperature gradients are generated both inside the pellets and between them. In this, way together with the pellets sintering, take place the sublimation - condensing transport of A 2B 6. Two multifunctional ceramic thin films could also be produced: the first one a thin film A 2B 6 operating as photo conducting film and the second one a porous ceramic thin film Cr 2O 3 operating as oxygen level regulator and as getter of impurities and of interstitial atoms from the A 2B 6 film.

We have realized photoconductive devices CdS:Cr 2O 3 and CdS,Se:Cr 2O 3 for a wide variety of multifunctional photoelectric sensors that can be applied to detecting the presence or the absence of an object, to connect or to disconnect automatically public illumination, to protect as a light screen a dangerous working space or a private property, etc. We have also the possibility to realized solar cells.

Network partners and their offer in the NMP field - KNOWLEDGE-BASED MULTIFUNCTIONAL MATERIALS and NEW PRODUCTION PROCESSES AND DEVICES

	National Institute of Materials Physics Title: Complex phenomena in ferroelectric based structures with enhanced or radically new properties Addresses: 3.4.2.1 Development of fundamental knowledge *Interfacial phenomena in materials – STREP* as well as 3.4.2.2 Technologies associated with the production, transformation and processing of knowledge-based multifunctional materials *Development of nanostructured porous materials* or *Multifunctional ceramic thin films with radically new properties* Name of the Network: Multifunctional materials and new production processes Organisation name: National Institute of Materials Physics Contact person,scientific title: Department: Laboratory of Semiconductor Physics and Complex Heterostructures Organisation’s address: Atomistilor 105bis Post code: 077125 City: Bucharest-Magurele Country: Romania Organisation type: national research institute Organisation size: medium, around 200 employees Web site:www.infim.ro E-mail address:[email protected] Telephone: +40-21-4930047/extension 230 Fax: +40-21-4930267 Brief description of the organization The National Institute of Materials Physics ( NIMP-Bucharest, Romania) came into being in 1977 under the name of Institute for Physics and Technology of Materials. The actual name was given in 1996 after a national accreditation procedure. Nowadays, the NIMP Bucharest is devoted to fundamental and applied research and development, with particular emphasis in the fields of solid state physics and materials research. Among the goals of the NIMP are: the preparation, characterization and study of the physical properties of new materials connected to high technology products and devices; the development of analytical techniques and methods applied in materials science; training of young scientists, PhD and MSc students; supply of both public institutions as well as companies with the Institute’s R&D know-how and expertise in the field of high-tech materials Brief description of involved Department The involved laboratory has an internationally recognized experience in: photoelectric phenomena in various materials and heterostructures; charge transport and trap investigation in bulk materials and thin films; ferroelectricity and related materials; field effect phenomena; radiation detectors, IR sensors. It possess a well equipped laboratory for complex electric/ferroelectric/photoelectric characterization of materials and structures, as well some facilities for thin film preparation using un-expensive chemical methods. *Abstract:* The large objective of the proposing group is to study in detail the properties of the ferroelectric materials and of the mixed ferroelectric-semiconductor structures (either multi-layers or nanocomposites). The proposed subject is covering several specific topics that, by themselves, can constitute the research object of a STREP. These are: Elucidating the role of interface grain boundaries in ferroelectric thin films and their effect on overall electric/ferroelectric properties of a metal-ferroelectric-metal (MFM) structure. It is a general mistake made by many peoples working in the field of ferroelectric thin films to ignore the grain boundaries or the other internal interfaces existing in ceramic films, and to consider them as homogeneous materials with well defined properties. That despite an overwhelming amount of experimental results showing that the properties of the films are very sensitive to the process conditions. Internal interfaces in thin ferroelectric films can introduce field and charge non-homogeneities affecting polarization switching and the leakage currents, as well the dielectric properties bringing extrinsic contributions to the dielectric constant. Porous ferroelectric materials and nano-composites for electromagnetic radiation detection. The aim is to develop not very expensive technologies for deposition of sufficiently thick, good quality films, to be used for light detection in domains from UV to IR. By mixing the nanoporous ferroelectric material with light sensitive semiconductor nano-crystals it is hoped to obtain nanocomposites with potentially enhanced propeties, or even with radically new properties in the field of optoelectronic. Ferroelectric, ceramic, thin films with radically new properties in the field of microelectronics. The goal is to obtain materials with high tunnability of the dielectric constant in both low frequency domain as well in the microwave domain. Another goal is to obtain materials with large values of the dielectric constant, useful for small size capacitors. Complex field effect devices with applications in optoelectronic. This is based on field effect photoconductivity, and includes study of the interface phenomena with and without light in complex heterostructures involving dielectric, ferroelectric, and semiconductor thin films and materials. Depending on the potential partners interest, the proposal can focus on one of the above objectives. Multifunctional ceramic thin films with radically new properties-STREP Multifunctional ceramic thin films obtained by sintering-sublimation method Name of the Network : Multifunctional materials and new production processes Organisation name : National Institute of Materials Physics Contact person scientific title: Dr. Igor Nazarenco Department: 170 Organisation’s address : Magurele, 105bis, Atomistilor str. Post code : 077125 City : Bucharest-Magurele Country : ROMANIA Organisation type : National Institute of Research@Development Organisation size : Medium Web site : www.infim.ro E-mail address : [email protected] Telephone : 401-4930195 Fax : 401-4930267 Brief description of the organization The National Institute of Materials Physics (NIMP) Bucharest ( Romania) is one of the physics institutes belonging to Institute of Atomic Physics (IFA-Bucharest-Magurele), one major research center in Romania. The general goal of the NIMP is to conduct high level basic and applied research in some selected areas of Solid State Physics and Materials Science. With a high qualified personnel (14 PhD supervisors, 89 Doctors, 54 PhD students), the NIMP is implied an important number of national and international R &D projects. Brief description of the involved Department: · investigation of semiconducting ceramics based on doped barium titanate for PTC thermistors and on manganites for NTC thermistors · studies of piezoelectric properties of bulk and thin films PZT · advanced piezocomposite materials of PZT-elastomer type · studies of spinel type ceramics for termosensitive magnetic transducers · photoelectric phenomena in semiconducting materials and heterostructures Abstract privind rezultatele si potentialul stiintific, tehnic, etc. in cadrul temei propuse in raport cu prevederile capitolelor 3.4.2. si 3.4.3 (max 1 pagina) Multifunctional ceramic thin films obtained by sintering-sublimation method The sintering-sublimation technique has been designed to increase the reliability of photoconducting devices mainly by decreasing the donors’ concentration which determines a high sensitivity. This method combines three different processes i.e. vacuum evaporation, thin layers growth from vapors and ceramic pellets sintering. Previous observations has shown that when sintering CdS ceramic pellets, transparent, high purity monocrystals condensed on the cooler parts of the oven. This process becomes more effective if are used pellets containing together with the raw A 2B 6 other component presenting a limited reactivity as nonstoichiometric chromium oxide. This oxide provide surfaces on which thin A 2B 6 layers are crystallizing. At the same time, the nonstoichiometric Cr 2O 3 can react with the oxygen allowing a more efficient control of the properties of the A 2B 6 thin film generated as a result of the above mentioned sublimation-condensing process. The process of film growth as well as the fast firing sintering take place simultaneously in a reductive atmosphere (a mixture of CO, CO 2 and N 2), specific to graphite crucibles, inhibits a further oxidation of A 2B 6 films and thus improves significantly their quality. This new method produce high reliability photo conducting ceramic films A 2B 6 onto a porous ceramic thin film Cr 2O 3 sustained by a Cd 2CrO 3 core, produced by the reaction between the nonstoichiometric Cr 2O 3 and interstitial Cd atoms. The thin ceramic polycrystalline films have been grown by using an installation similar to those used to grow crystals by the Bridgman method. It consists of a crucible made of nuclear graphite fixed on a rod which executes an oscillating movement combined with a slow rotation (10 rpm) along the axis of a vertical oven. The distribution of the temperature along the oven axis is characterized by the presence of two steps corresponding to each extremity. Between these steps, the temperature increase monotonously with a medium gradient equal to 100 K cm -1. As a result of the crucible displacement within the oven, transitory temperature gradients are generated both inside the pellets and between them. In this, way together with the pellets sintering, take place the sublimation - condensing transport of A 2B 6. Two multifunctional ceramic thin films could also be produced: the first one a thin film A 2B 6 operating as photo conducting film and the second one a porous ceramic thin film Cr 2O 3 operating as oxygen level regulator and as getter of impurities and of interstitial atoms from the A 2B 6 film. We have realized photoconductive devices CdS:Cr 2O 3 and CdS,Se:Cr 2O 3 for a wide variety of multifunctional photoelectric sensors that can be applied to detecting the presence or the absence of an object, to connect or to disconnect automatically public illumination, to protect as a light screen a dangerous working space or a private property, etc. We have also the possibility to realized solar cells.