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12 pages, 3269 KiB

Open AccessArticle

SiGeSn Quantum Dots in HfO₂ for Floating Gate Memory Capacitors

by Catalin Palade, Adrian Slav, Ovidiu Cojocaru, Valentin Serban Teodorescu, Toma Stoica, Magdalena Lidia Ciurea and Ana-Maria Lepadatu

Coatings 2022, 12(3), 348; https://doi.org/10.3390/coatings12030348 - 07 Mar 2022

Cited by 5 | Viewed by 2380

Abstract

Group IV quantum dots (QDs) in HfO₂ are attractive for non-volatile memories (NVMs) due to complementary metal-oxide semiconductor (CMOS) compatibility. Besides the role of charge storage centers, SiGeSn QDs have the advantage of a low thermal budget for formation, because Sn presence [...] Read more.

Group IV quantum dots (QDs) in HfO₂ are attractive for non-volatile memories (NVMs) due to complementary metal-oxide semiconductor (CMOS) compatibility. Besides the role of charge storage centers, SiGeSn QDs have the advantage of a low thermal budget for formation, because Sn presence decreases crystallization temperature, while Si ensures higher thermal stability. In this paper, we prepare MOS capacitors based on 3-layer stacks of gate HfO₂/floating gate of SiGeSn QDs in HfO₂/tunnel HfO₂/p-Si obtained by magnetron sputtering deposition followed by rapid thermal annealing (RTA) for nanocrystallization. Crystalline structure, morphology, and composition studies by cross-section transmission electron microscopy and X-ray diffraction correlated with Raman spectroscopy and C–V measurements are carried out for understanding RTA temperature effects on charge storage behavior. 3-layer morphology and Sn content trends with RTA temperature are explained by the strongly temperature-dependent Sn segregation and diffusion processes. We show that the memory properties measured on Al/3-layer stack/p-Si/Al capacitors are controlled by SiGeSn-related trapping states (deep electronic levels) and low-ordering clusters for RTA at 325–450 °C, and by crystalline SiGeSn QDs for 520 and 530 °C RTA. Specific to the structures annealed at 520 and 530 °C is the formation of two kinds of crystalline SiGeSn QDs, i.e., QDs with low Sn content (2 at.%) that are positioned inside the floating gate, and QDs with high Sn content (up to 12.5 at.%) located at the interface of floating gate with adjacent HfO₂ layers. The presence of Sn in the SiGe intermediate layer decreases the SiGe crystallization temperature and induces the easier crystallization of the diamond structure in comparison with 3-layer stacks with Ge-HfO₂ intermediate layer. High frequency-independent memory windows of 3–4 V and stored electron densities of 1–2 × 10¹³ electrons/cm² are achieved. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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9 pages, 2074 KiB

Open AccessFeature PaperArticle

Exchange Bias Effect in LaFeO₃: La_0.7Ca_0.3MnO₃ Composite Thin Films

by Feng Wang, Wei Fu, Chengming Jiang, Junxiao Li and Jijie Huang

Coatings 2021, 11(9), 1125; https://doi.org/10.3390/coatings11091125 - 16 Sep 2021

Cited by 2 | Viewed by 1899

Abstract

Composite thin films arouse great interests owing to the multifunctionalities and heterointerface induced physical property tailoring. The exchange bias effect aroused from the ferromagnetic (FM)–antiferromagnetic (AFM) heterointerface is applicable in various applications such as magnetic storage. In this work, (LaFeO₃)_x [...] Read more.

Composite thin films arouse great interests owing to the multifunctionalities and heterointerface induced physical property tailoring. The exchange bias effect aroused from the ferromagnetic (FM)–antiferromagnetic (AFM) heterointerface is applicable in various applications such as magnetic storage. In this work, (LaFeO₃)_x:(La_0.7Ca_0.3MnO₃)_1−x composite thin films have been deposited via pulsed laser deposition (PLD) and the exchange bias effect was investigated. In such system, LaFeO₃ (LFO) is an antiferromagnet while La_0.7Ca_0.3MnO₃ (LCMO) is a ferromagnet, which results in the exchange bias interfacial coupling at the FM/AFM interface. The composition variation of the two phases could lead to the exchange bias field (H_EB) tuning in the composite system. This work demonstrates a new composite thin film system with FM-AFM interfacial exchange coupling, which could be applied in various spintronic applications. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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12 pages, 4591 KiB

Open AccessArticle

Structure and Characterization of TiC/GLC Multilayered Films with Various Bilayers Periods

by Weiqi Wang, Xiaoming Ling, Rui Wang, Wenhao Nie, Li Ji and Hongxuan Li

Coatings 2021, 11(7), 787; https://doi.org/10.3390/coatings11070787 - 30 Jun 2021

Cited by 1 | Viewed by 1631

Abstract

The spontaneously self-organizing multilayered graphite-like carbon (denoted as GLC) /TiC films with various bilayer periods in the range of 13.3–17.5 nm were deposited on silicon and 1Cr18Mn8Ni5N stainless steel substrates using closed field magnetron sputtering deposition facility. The microstructures and chemical compositions of [...] Read more.

The spontaneously self-organizing multilayered graphite-like carbon (denoted as GLC) /TiC films with various bilayer periods in the range of 13.3–17.5 nm were deposited on silicon and 1Cr18Mn8Ni5N stainless steel substrates using closed field magnetron sputtering deposition facility. The microstructures and chemical compositions of the prepared multilayered films were characterized by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy respectively. The self-organizing multilayered structures in all of the films consisted of titanium carbide layers and sp²-rich carbon layers periodically alternate arrangement. The TiC contents and bilayer periods of the multilayered films can be controlled by means of adjusting of sputtering current of graphite target. Furthermore, the mechanical and tribological performances of the prepared films were appraised by nano-indentor, scratch measures, and ball-on-plate tribometer respectively. The results indicated that multilayer structure endowed the as-deposited TiC/GLC films outstanding mechanical and tribological properties, especially the multilayer film with 15.9 nm bilayer period deposited at 10 A sputtering current showed the excellent adhesion strength and hardness; Simultaneously it also exhibited the lowest average friction coefficient in the humid environment owing to its high content of sp² hybrid carbon. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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9 pages, 1938 KiB

Open AccessFeature PaperArticle

Epitaxial Growth and Stoichiometry Control of Ultrawide Bandgap ZnGa₂O₄ Films by Pulsed Laser Deposition

by Liu Wang, Wenrui Zhang, Ningtao Liu, Tan Zhang, Zilong Wang, Simiao Wu, Zhaolin Zhan and Jichun Ye

Coatings 2021, 11(7), 782; https://doi.org/10.3390/coatings11070782 - 30 Jun 2021

Cited by 8 | Viewed by 2030

Abstract

ZnGa₂O₄ is a promising semiconductor for developing high-performance deep-ultraviolet photodetectors owing to a number of advantageous fundamental characteristics. However, Zn volatilization during the ZnGa₂O₄ growth is a widely recognized problem that seriously degrades the film quality and [...] Read more.

ZnGa₂O₄ is a promising semiconductor for developing high-performance deep-ultraviolet photodetectors owing to a number of advantageous fundamental characteristics. However, Zn volatilization during the ZnGa₂O₄ growth is a widely recognized problem that seriously degrades the film quality and the device performance. In this study, we report the synthesis of epitaxial ZnGa₂O₄ thin films by pulsed laser deposition using a non-stoichiometric Zn_1+xGa₂O₄ target. It is found that supplementing excessive Zn concentration from the target is highly effective to stabilize stochiometric ZnGa₂O₄ thin films during the PLD growth. The influence of various growth parameters on the phase formation, crystallinity and surface morphology is systematically investigated. The film growth behavior further impacts the resulting optical absorption and thermal conductivity. The optimized epitaxial ZnGa₂O₄ film exhibits a full width at half maximum value of 0.6 degree for a 120 nm thickness, a surface roughness of 0.223 nm, a band gap of 4.79 eV and a room-temperature thermal conductivity of 40.137 W/(m⋅K). This study provides insights into synthesizing epitaxial ZnGa₂O₄ films for high performance optoelectronic devices. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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14 pages, 5684 KiB

Open AccessArticle

Tuning the Optical Properties of MEH–PPV/PFO Hybrid Thin Films via the Incorporation of CsPbBr₃ Quantum Dots

by Saif M. H. Qaid, Bandar Ali Al-Asbahi, Hamid M. Ghaithan and Abdullah S. Aldwayyan

Coatings 2021, 11(2), 154; https://doi.org/10.3390/coatings11020154 - 29 Jan 2021

Cited by 8 | Viewed by 2252

Abstract

The current work examines the effects of cesium lead bromide (CsPbBr₃) perovskite quantum dots (PQDs) on the structural and optical properties of conjugated polymer blends of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH–PPV) and poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO). MEH–PPV/PFO composite thin-films containing PQDs with weight [...] Read more.

The current work examines the effects of cesium lead bromide (CsPbBr₃) perovskite quantum dots (PQDs) on the structural and optical properties of conjugated polymer blends of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH–PPV) and poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO). MEH–PPV/PFO composite thin-films containing PQDs with weight ratios between 0.5 wt.% and 10 wt.% were prepared via a solution-blending method prior to spin-coating on glass substrates. The MEH–PPV/PFO composites’ crystallinity was improved, and the roughness was dramatically increased with higher PQDs content, as confirmed by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Conversely, a higher PQDs content resulted in a gradual reduction of the Urbach tail and an increase in the steepness parameter, thereby reducing the localized density of the electronic states within the forbidden bandgap of the hybrids. Moreover, a slight reduction in the direct and indirect bandgaps was found in PQDs/(MEH–PPV/PFO) composite films containing a higher PQDs content and provided evidence of the low concentration of the localized states. The incorporation of the PQDs resulted in enhanced non-radiative energy transfer processes in the MEH–PPV/PFO hybrids, which are very important for the development of optimized optoelectronic devices. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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Review

Jump to: Research

24 pages, 5859 KiB

Open AccessReview

Recent Studies on the Fabrication of Multilayer Films by Magnetron Sputtering and Their Irradiation Behaviors

by Jinyang Ni, Jin Li, Jie Jian, Jianchao He, Hongsheng Chen, Xuesong Leng and Xiangli Liu

Coatings 2021, 11(12), 1468; https://doi.org/10.3390/coatings11121468 - 29 Nov 2021

Cited by 5 | Viewed by 2386

Abstract

Multilayer films with high-density layer interfaces have been studied widely because of the unique mechanical and functional properties. Magnetron sputtering is widely chosen to fabricate multilayer films because of the convenience in controlling the microstructure. Essentially, the properties of multilayer films are decided [...] Read more.

Multilayer films with high-density layer interfaces have been studied widely because of the unique mechanical and functional properties. Magnetron sputtering is widely chosen to fabricate multilayer films because of the convenience in controlling the microstructure. Essentially, the properties of multilayer films are decided by the microstructure, which could be adjusted by manipulating the deposition parameters, such as deposition temperature, rate, bias, and target–substrate distance, during the sputter process. In this review, the influences of the deposition parameters on the microstructure evolution of the multilayer films have been summarized. Additionally, the impacts of individual layer thickness on the microstructure evolution as well as the irradiation behavior of various multilayer films have been discussed. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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23 pages, 6095 KiB

Open AccessReview

Ferroelectric and Ferroelastic Domain Related Formation and Influential Mechanisms of Vapor Deposited Piezoelectric Thin Films

by Chu Chen, Jian Song, Qi Zhang, Mingyu Gong, Yue Liu and Tongxiang Fan

Coatings 2021, 11(12), 1437; https://doi.org/10.3390/coatings11121437 - 24 Nov 2021

Cited by 4 | Viewed by 1935

Abstract

Compared to the bulk piezoelectric materials counterpart, piezoelectric thin films (PTFs) possess advantages of smaller size, lower power consumption, better sensitivity, and have broad application in advanced micro-electro-mechanical system (MEMS) devices. However, the performance of MEMS transducers and actuators are largely limited by [...] Read more.

Compared to the bulk piezoelectric materials counterpart, piezoelectric thin films (PTFs) possess advantages of smaller size, lower power consumption, better sensitivity, and have broad application in advanced micro-electro-mechanical system (MEMS) devices. However, the performance of MEMS transducers and actuators are largely limited by PTFs piezoelectric properties. In this review, we focus on understanding structure-property relationship of vapor deposited PTFs, with emphasis on the effect of strain energy and electrostatic energy in thin films, especially, energy relaxation induced misfit dislocation and ferroelectric (FS) and ferroelastic (FC) domain formation mechanisms. We then discuss the microstructure of these domains and their influential mechanisms on piezoelectric properties, as well as the domain engineering strategies (i.e., internal and external stimuli). This review will motivate further experimental, theoretical, and simulation studies on FS and FC domain engineering in PTFs. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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22 pages, 3743 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Synthesis, Microstructure and Properties of Magnetron Sputtered Lead Zirconate Titanate (PZT) Thin Film Coatings

by Youcao Ma, Jian Song, Xubo Wang, Yue Liu and Jia Zhou

Coatings 2021, 11(8), 944; https://doi.org/10.3390/coatings11080944 - 07 Aug 2021

Cited by 19 | Viewed by 4521

Abstract

Compared to aluminum nitride (AlN) with simple stoichiometry, lead zirconate titanate thin films (PZT) are the other promising candidate in advanced micro-electro-mechanical system (MEMS) devices due to their excellent piezoelectric and dielectric properties. The fabrication of PZT thin films with a large area [...] Read more.

Compared to aluminum nitride (AlN) with simple stoichiometry, lead zirconate titanate thin films (PZT) are the other promising candidate in advanced micro-electro-mechanical system (MEMS) devices due to their excellent piezoelectric and dielectric properties. The fabrication of PZT thin films with a large area is challenging but in urgent demand. Therefore, it is necessary to establish the relationships between synthesis parameters and specific properties. Compared to sol-gel and pulsed laser deposition techniques, this review highlights a magnetron sputtering technique owing to its high feasibility and controllability. In this review, we survey the microstructural characteristics of PZT thin films, as well as synthesis parameters (such as substrate, deposition temperature, gas atmosphere, and annealing temperature, etc.) and functional proper-ties (such as dielectric, piezoelectric, and ferroelectric, etc). The dependence of these influential factors is particularly emphasized in this review, which could provide experimental guidance for researchers to acquire PZT thin films with expected properties by a magnetron sputtering technique. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

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