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Materials, Volume 5, Issue 3 (March 2012), Pages 364-557

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Research

Jump to: Review

Open AccessArticle X-ray Photoelectron Spectroscopy (XPS) Depth Profiling for Evaluation of La2Zr2O7 Buffer Layer Capacity
Materials 2012, 5(3), 364-376; doi:10.3390/ma5030364
Received: 1 February 2012 / Accepted: 21 February 2012 / Published: 27 February 2012
Cited by 12 | PDF Full-text (605 KB) | HTML Full-text | XML Full-text
Abstract
Lanthanum zirconate (LZO) films from water-based precursors were deposited on Ni-5%W tape by chemical solution deposition. The buffer capacity of these layers includes the prevention of Ni oxidation of the substrate and Ni penetration towards the YBCO film which is detrimental for the
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Lanthanum zirconate (LZO) films from water-based precursors were deposited on Ni-5%W tape by chemical solution deposition. The buffer capacity of these layers includes the prevention of Ni oxidation of the substrate and Ni penetration towards the YBCO film which is detrimental for the superconducting properties. X-ray Photoelectron Spectroscopy depth profiling was used to study the barrier efficiency before and after an additional oxygen annealing step, which simulates the thermal treatment for YBCO thin film synthesis. Measurements revealed that the thermal treatment in presence of oxygen could severely increase Ni diffusion. Nonetheless it was shown that from the water-based precursors’ buffer layers with sufficient barrier capacity towards Ni penetration could be synthesized if the layers meet a certain critical thickness and density. Full article
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Open AccessArticle A Study of Trimethylsilane (3MS) and Tetramethylsilane (4MS) Based α-SiCN:H/α-SiCO:H Diffusion Barrier Films
Materials 2012, 5(3), 377-384; doi:10.3390/ma5030377
Received: 19 December 2011 / Revised: 31 January 2012 / Accepted: 15 February 2012 / Published: 2 March 2012
Cited by 4 | PDF Full-text (210 KB) | HTML Full-text | XML Full-text
Abstract
Amorphous nitrogen-doped silicon carbide (α-SiCN:H) films have been used as a Cu penetration diffusion barrier and interconnect etch stop layer in the below 90-nanometer ultra-large scale integration (ULSI) manufacturing technology. In this study, the etching stop layers were deposited by using trimethylsilane (3MS)
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Amorphous nitrogen-doped silicon carbide (α-SiCN:H) films have been used as a Cu penetration diffusion barrier and interconnect etch stop layer in the below 90-nanometer ultra-large scale integration (ULSI) manufacturing technology. In this study, the etching stop layers were deposited by using trimethylsilane (3MS) or tetramethylsilane (4MS) with ammonia by plasma-enhanced chemical vapor deposition (PECVD) followed by a procedure for tetra-ethoxyl silane (TEOS) oxide. The depth profile of Cu distribution examined by second ion mass spectroscopy (SIMs) showed that 3MS α-SiCN:H exhibited a better barrier performance than the 4MS film, which was revealed by the Cu signal. The FTIR spectra also showed the intensity of Si-CH3 stretch mode in the α-SiCN:H film deposited by 3MS was higher than that deposited by 4MS. A novel multi structure of oxygen-doped silicon carbide (SiC:O) substituted TEOS oxide capped on 4MS α-SiC:N film was also examined. In addition to this, the new multi etch stop layers can be deposited together with the same tool which can thus eliminate the effect of the vacuum break and accompanying environmental contamination. Full article
(This article belongs to the Special Issue Low k Dielectic Materials)
Open AccessArticle Elaboration of Prussian Blue Analogue/Silica Nanocomposites: Towards Tailor-Made Nano-Scale Electronic Devices
Materials 2012, 5(3), 385-403; doi:10.3390/ma5030385
Received: 19 January 2012 / Revised: 20 February 2012 / Accepted: 20 February 2012 / Published: 5 March 2012
Cited by 11 | PDF Full-text (2795 KB) | HTML Full-text | XML Full-text
Abstract
The research of new molecular materials able to replace classical solid materials in electronics has attracted growing attention over the past decade. Among these compounds photoswitchable Prussian blue analogues (PBA) are particularly interesting for the elaboration of new optical memories. However these coordination
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The research of new molecular materials able to replace classical solid materials in electronics has attracted growing attention over the past decade. Among these compounds photoswitchable Prussian blue analogues (PBA) are particularly interesting for the elaboration of new optical memories. However these coordination polymers are generally synthesised as insoluble powders that cannot be integrated into a real device. Hence their successful integration into real applications depends on an additional processing step. Nanostructured oxides elaborated by sol-gel chemistry combined with surfactant micelle templating can be used as nanoreactors to confine PBA precipitation and organize the functional nano-objects in the three dimensions of space. In this work we present the elaboration of different CoFe PBA/silica nanocomposites. Our synthetic procedure fully controls the synthesis of PBA in the porosity of the silica matrix from the insertion of the precursors up to the formation of the photomagnetic compound. We present results on systems from the simplest to the most elaborate: from disordered xerogels to ordered nanostructured films passing through mesoporous monoliths. Full article
(This article belongs to the Special Issue Advances in Porous Inorganic Materials)
Open AccessArticle Initial Processes of Atomic Layer Deposition of Al2O3 on InGaAs: Interface Formation Mechanisms and Impact on Metal-Insulator-Semiconductor Device Performance
Materials 2012, 5(3), 404-414; doi:10.3390/ma5030404
Received: 7 December 2011 / Revised: 18 January 2012 / Accepted: 4 March 2012 / Published: 8 March 2012
Cited by 12 | PDF Full-text (1020 KB) | HTML Full-text | XML Full-text
Abstract
Interface-formation processes in atomic layer deposition (ALD) of Al2O3on InGaAs surfaces were investigated using on-line Auger electron spectroscopy. Al2O3 ALD was carried out by repeating a cycle of Al(CH3)3 (trimethylaluminum, TMA) adsorption and
[...] Read more.
Interface-formation processes in atomic layer deposition (ALD) of Al2O3 on InGaAs surfaces were investigated using on-line Auger electron spectroscopy. Al2O3 ALD was carried out by repeating a cycle of Al(CH3)3 (trimethylaluminum, TMA) adsorption and oxidation by H2O. The first two ALD cycles increased the Al KLL signal, whereas they did not increase the O KLL signal. Al2O3 bulk-film growth started from the third cycle. These observations indicated that the Al2O3/InGaAs interface was formed by reduction of the surface oxides with TMA. In order to investigate the effect of surface-oxide reduction on metal-insulator-semiconductor (MIS) properties, capacitors and field-effect transistors (FETs) were fabricated by changing the TMA dosage during the interface formation stage. The frequency dispersion of the capacitance-voltage characteristics was reduced by employing a high TMA dosage. The high TMA dosage, however, induced fixed negative charges at the MIS interface and degraded channel mobility. Full article
(This article belongs to the Special Issue High-k Materials and Devices)
Open AccessArticle Template-Based Geometric Simulation of Flexible Frameworks
Materials 2012, 5(3), 415-431; doi:10.3390/ma5030415
Received: 26 January 2012 / Revised: 26 February 2012 / Accepted: 1 March 2012 / Published: 12 March 2012
Cited by 8 | PDF Full-text (933 KB)
Abstract
Specialised modelling and simulation methods implementing simplified physical models are valuable generators of insight. Template-based geometric simulation is a specialised method for modelling flexible framework structures made up of rigid units. We review the background, development and implementation of the method, and its
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Specialised modelling and simulation methods implementing simplified physical models are valuable generators of insight. Template-based geometric simulation is a specialised method for modelling flexible framework structures made up of rigid units. We review the background, development and implementation of the method, and its applications to the study of framework materials such as zeolites and perovskites. The “flexibility window” property of zeolite frameworks is a particularly significant discovery made using geometric simulation. Software implementing geometric simulation of framework materials, “GASP”, is freely available to researchers. Full article
(This article belongs to the Special Issue Computer Modelling of Microporous Materials)
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Open AccessArticle Formation of Indium-Doped Zinc Oxide Thin Films Using Ultrasonic Spray Pyrolysis: The Importance of the Water Content in the Aerosol Solution and the Substrate Temperature for Enhancing Electrical Transport
Materials 2012, 5(3), 432-442; doi:10.3390/ma5030432
Received: 5 January 2012 / Revised: 10 February 2012 / Accepted: 29 February 2012 / Published: 12 March 2012
Cited by 11 | PDF Full-text (435 KB) | HTML Full-text | XML Full-text
Abstract
Indium doped zinc oxide [ZnO:In] thin films have been deposited at 430°C on soda-lime glass substrates by the chemical spray technique, starting from zinc acetate and indium acetate. Pulverization of the solution was done by ultrasonic excitation. The variations in the electrical, structural,
[...] Read more.
Indium doped zinc oxide [ZnO:In] thin films have been deposited at 430°C on soda-lime glass substrates by the chemical spray technique, starting from zinc acetate and indium acetate. Pulverization of the solution was done by ultrasonic excitation. The variations in the electrical, structural, optical, and morphological characteristics of ZnO:In thin films, as a function of both the water content in the starting solution and the substrate temperature, were studied. The electrical resistivity of ZnO:In thin films is not significantly affected with the increase in the water content, up to 200 mL/L; further increase in water content causes an increase in the resistivity of the films. All films show a polycrystalline character, fitting well with the hexagonal ZnO wurtzite-type structure. No preferential growth in samples deposited with the lowest water content was observed, whereas an increase in water content gave rise to a (002) growth. The surface morphology of the films shows a consistency with structure results, as non-geometrical shaped round grains were observed in the case of films deposited with the lowest water content, whereas hexagonal slices, with a wide size distribution were observed in the other cases. In addition, films deposited with the highest water content show a narrow size distribution. Full article
(This article belongs to the Special Issue Advances in Transparent Conducting Oxides)
Open AccessArticle Oriented Collagen Scaffolds for Tissue Engineering
Materials 2012, 5(3), 501-511; doi:10.3390/ma5030501
Received: 25 February 2012 / Revised: 6 March 2012 / Accepted: 8 March 2012 / Published: 16 March 2012
Cited by 10 | PDF Full-text (1300 KB) | HTML Full-text | XML Full-text
Abstract
Oriented collagen scaffolds were developed in the form of sheet, mesh and tube by arraying flow-oriented collagen string gels and dehydrating the arrayed gels. The developed collagen scaffolds can be any practical size with any direction of orientation for tissue engineering applications. The
[...] Read more.
Oriented collagen scaffolds were developed in the form of sheet, mesh and tube by arraying flow-oriented collagen string gels and dehydrating the arrayed gels. The developed collagen scaffolds can be any practical size with any direction of orientation for tissue engineering applications. The birefringence of the collagen scaffolds was quantitatively analyzed by parallel Nicols method. Since native collagen in the human body has orientations such as bone, cartilage, tendon and cornea, and the orientation has a special role for the function of human organs, the developed various types of three-dimensional oriented collagen scaffolds are expected to be useful biomaterials for tissue engineering and regenerative medicines. Full article
(This article belongs to the Special Issue Fibrous Scaffolds for Tissue Engineering)
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Open AccessArticle Exact Solution of a Constraint Optimization Problem for the Thermoelectric Figure of Merit
Materials 2012, 5(3), 528-539; doi:10.3390/ma5030528
Received: 13 January 2012 / Revised: 15 March 2012 / Accepted: 19 March 2012 / Published: 21 March 2012
Cited by 2 | PDF Full-text (158 KB) | HTML Full-text | XML Full-text
Abstract
In the classical theory of thermoelectricity, the performance integrals for a fully self-compatible material depend on the dimensionless figure of merit zT. Usually these integrals are evaluated for constraints z = const. and zT = const., respectively. In this paper we discuss
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In the classical theory of thermoelectricity, the performance integrals for a fully self-compatible material depend on the dimensionless figure of merit zT. Usually these integrals are evaluated for constraints z = const. and zT = const., respectively. In this paper we discuss the question from a mathematical point of view whether there is an optimal temperature characteristics of the figure of merit. We solve this isoperimetric variational problem for the best envelope of a family of curves z(T)T. Full article
(This article belongs to the Special Issue Advances in Functionally Graded Materials)
Open AccessArticle Novel Textile Scaffolds Generated by Flock Technology for Tissue Engineering of Bone and Cartilage
Materials 2012, 5(3), 540-557; doi:10.3390/ma5030540
Received: 22 December 2011 / Revised: 7 March 2012 / Accepted: 12 March 2012 / Published: 22 March 2012
Cited by 6 | PDF Full-text (1138 KB) | HTML Full-text | XML Full-text
Abstract
Textile scaffolds can be found in a variety of application areas in regenerative medicine and tissue engineering. In the present study we used electrostatic flocking—a well-known textile technology—to produce scaffolds for tissue engineering of bone. Flock scaffolds stand out due to their unique
[...] Read more.
Textile scaffolds can be found in a variety of application areas in regenerative medicine and tissue engineering. In the present study we used electrostatic flocking—a well-known textile technology—to produce scaffolds for tissue engineering of bone. Flock scaffolds stand out due to their unique structure: parallel arranged fibers that are aligned perpendicularly to a substrate, resulting in mechanically stable structures with a high porosity. In compression tests we demonstrated good mechanical properties of such scaffolds and in cell culture experiments we showed that flock scaffolds allow attachment and proliferation of human mesenchymal stem cells and support their osteogenic differentiation. These matrices represent promising scaffolds for tissue engineering. Full article
(This article belongs to the Special Issue Fibrous Scaffolds for Tissue Engineering)
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Review

Jump to: Research

Open AccessReview Comprehensive Study of Lanthanum Aluminate High-Dielectric-Constant Gate Oxides for Advanced CMOS Devices
Materials 2012, 5(3), 443-477; doi:10.3390/ma5030443
Received: 7 January 2012 / Revised: 8 February 2012 / Accepted: 6 March 2012 / Published: 14 March 2012
Cited by 13 | PDF Full-text (1413 KB) | HTML Full-text | XML Full-text
Abstract
A comprehensive study of the electrical and physical characteristics of Lanthanum Aluminate (LaAlO3) high-dielectric-constant gate oxides for advanced CMOS devices was performed. The most distinctive feature of LaAlO3 as compared with Hf-based high-k materials is the thermal stability at
[...] Read more.
A comprehensive study of the electrical and physical characteristics of Lanthanum Aluminate (LaAlO3) high-dielectric-constant gate oxides for advanced CMOS devices was performed. The most distinctive feature of LaAlO3 as compared with Hf-based high-k materials is the thermal stability at the interface with Si, which suppresses the formation of a low-permittivity Si oxide interfacial layer. Careful selection of the film deposition conditions has enabled successful deposition of an LaAlO3 gate dielectric film with an equivalent oxide thickness (EOT) of 0.31 nm. Direct contact with Si has been revealed to cause significant tensile strain to the Si in the interface region. The high stability of the effective work function with respect to the annealing conditions has been demonstrated through comparison with Hf-based dielectrics. It has also been shown that the effective work function can be tuned over a wide range by controlling the La/(La + Al) atomic ratio. In addition, gate-first n-MOSFETs with ultrathin EOT that use sulfur-implanted Schottky source/drain technology have been fabricated using a low-temperature process. Full article
(This article belongs to the Special Issue High-k Materials and Devices)
Open AccessReview Ultimate Scaling of High-κ Gate Dielectrics: Higher-κ or Interfacial Layer Scavenging?
Materials 2012, 5(3), 478-500; doi:10.3390/ma5030478
Received: 29 January 2012 / Revised: 11 February 2012 / Accepted: 6 March 2012 / Published: 14 March 2012
Cited by 54 | PDF Full-text (597 KB) | HTML Full-text | XML Full-text
Abstract
Current status and challenges of aggressive equivalent-oxide-thickness (EOT) scaling of high-κ gate dielectrics via higher-κ ( > 20) materials and interfacial layer (IL) scavenging techniques are reviewed. La-based higher-κ materials show aggressive EOT scaling (0.5–0.8 nm), but with effective workfunction (EWF) values suitable
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Current status and challenges of aggressive equivalent-oxide-thickness (EOT) scaling of high-κ gate dielectrics via higher-κ ( > 20) materials and interfacial layer (IL) scavenging techniques are reviewed. La-based higher-κ materials show aggressive EOT scaling (0.5–0.8 nm), but with effective workfunction (EWF) values suitable only for n-type field-effect-transistor (FET). Further exploration for p-type FET-compatible higher-κ materials is needed. Meanwhile, IL scavenging is a promising approach to extend Hf-based high-κ dielectrics to future nodes. Remote IL scavenging techniques enable EOT scaling below 0.5 nm. Mobility-EOT trends in the literature suggest that short-channel performance improvement is attainable with aggressive EOT scaling via IL scavenging or La-silicate formation. However, extreme IL scaling (e.g., zero-IL) is accompanied by loss of EWF control and with severe penalty in reliability. Therefore, highly precise IL thickness control in an ultra-thin IL regime ( < 0.5 nm) will be the key technology to satisfy both performance and reliability requirements for future CMOS devices. Full article
(This article belongs to the Special Issue High-k Materials and Devices)
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Open AccessReview Study of Direct-Contact HfO2/Si Interfaces
Materials 2012, 5(3), 512-527; doi:10.3390/ma5030512
Received: 27 February 2012 / Revised: 5 March 2012 / Accepted: 8 March 2012 / Published: 19 March 2012
Cited by 16 | PDF Full-text (881 KB) | HTML Full-text | XML Full-text
Abstract
Controlling monolayer Si oxide at the HfO2/Si interface is a challenging issue in scaling the equivalent oxide thickness of HfO2/Si gate stack structures. A concept that the author proposes to control the Si oxide interface by using ultra-high vacuum
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Controlling monolayer Si oxide at the HfO2/Si interface is a challenging issue in scaling the equivalent oxide thickness of HfO2/Si gate stack structures. A concept that the author proposes to control the Si oxide interface by using ultra-high vacuum electron-beam HfO2 deposition is described in this review paper, which enables the so-called direct-contact HfO2/Si structures to be prepared. The electrical characteristics of the HfO2/Si metal-oxide-semiconductor capacitors are reviewed, which suggest a sufficiently low interface state density for the operation of metal-oxide-semiconductor field-effect-transistors (MOSFETs) but reveal the formation of an unexpected strong interface dipole. Kelvin probe measurements of the HfO2/Si structures provide obvious evidence for the formation of dipoles at the HfO2/Si interfaces. The author proposes that one-monolayer Si-O bonds at the HfO2/Si interface naturally lead to a large potential difference, mainly due to the large dielectric constant of the HfO2. Dipole scattering is demonstrated to not be a major concern in the channel mobility of MOSFETs. Full article
(This article belongs to the Special Issue High-k Materials and Devices)

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