Ultrathin Fe films on Cu͑111͒ have been grown by pulsed-laser deposition ͑PLD͒ whose instantaneous deposition rate is about six orders of magnitude larger than that of the conventional molecular-beam epitaxy based on thermal deposition ͑TD͒. Compared to the TD prepared Fe/Cu͑111͒ films, the PLD films have a significantly improved layer-by-layer morphology and a substantially enhanced stability of the fcc phase as characterized by scanning tunneling microscopy and electron-diffraction techniques. The magnetic properties of the PLD films, investigated by magneto-optical Kerr effect, also show remarkably different behavior as compared to the TD films. At low thickness ͑Ͻ3 ML͒, while the TD films are characterized by a low net moment and a short-range ferromagnetic order, the PLD films show a high net moment with a true long-range ferromagnetic order. Above 3 ML both PLD and TD films undergo a magnetic transition though with apparently different structural origin. We discuss these results based on the different growth and structure between the PLD and TD grown Fe films.

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Multiferroic heterostructures composed of complex oxide thin films and ferroelectric single crystals have aroused considerable interest due to the electrically switchable strain and charge elements of oxide films by the polarization reversal of ferroelectrics. Previous studies have demonstrated that the electric‐field‐control of physical properties of such heterostructures is exclusively due to the ferroelectric domain switching‐induced lattice strain effects. Here, the first successful integration of the hexagonal ZnO:Mn dilute magnetic semiconductor thin films with high performance (111)‐oriented perovskite Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) single crystals is reported, and unprecedented charge‐mediated electric‐field control of both electronic transport and ferromagnetism at room temperature for PMN‐PT single crystal‐based oxide heterostructures is realized. A significant carrier concentration‐tunability of resistance and magnetization by ≈400% and ≈257% is achieved at room temperature. The electric‐field controlled bistable resistance and ferromagnetism switching at room temperature via interfacial electric charge presents a potential strategy for designing prototype devices for information storage. The results also disclose that the relative importance of the strain effect and interfacial charge effect in oxide film/ferroelectric crystal heterostructures can be tuned by appropriately adjusting the charge carrier density of oxide films.

counterparts. [2] Therefore, 2D materials are ideal for flexible optoelectronics and have the potential to be used in the next-generation ultrathin electronic and optoelectronic devices. [1] The concept of 2D materials was first realized when graphene was found in 2004. [4] Graphene has attracted extensive attention for its excellent electrical, optical, and mechanical properties. [4][5][6] They have been investigated for various technological applications, including spintronics, sensors, optoelectronics, supercapacitors, and solar cells, etc. [5,7] Besides graphene, other 2D materials, such as h-BN, phosphorene, silicene, germanene, and transition metal dichalcogenides (molybdenum disulfide (MoS 2 ), molybdenum diselenide (MoSe 2 ), tungsten disulfide (WS 2 ), and tungsten diselenide (WSe 2 ), etc.), have been studied extensively in recent years. [1,[8][9][10][11] The thickness of single-layer 2D materials is usually on the order or less than 1 nm. At the same time, their lateral sizes could reach much larger size (from microns to even inches), and 2D materials can be transferred to different substrates before subsequent processing or follow-up measurements for characterizations or device applications.Strain engineering is a promising way to tune the electrical, electrochemical, magnetic, and optical properties of 2D materials, with the potential to achieve high-performance 2D-material-based devices ultimately. This review discusses the experimental and theoretical results from recent advances in the strain engineering of 2D materials. Some novel methods to induce strain are summarized and then the tunable electrical and optical/optoelectronic properties of 2D materials via strain engineering are highlighted, including particularly the previously less-discussed strain tuning of superconducting, magnetic, and electrochemical properties. Also, future perspectives of strain engineering are given for its potential applications in functional devices. The state of the survey presents the ever-increasing advantages and popularity of strain engineering for tuning properties of 2D materials. Suggestions and insights for further research and applications in optical, electronic, and spintronic devices are provided.

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Published by the AIP Publishing Articles you may be interested inInfluence of lattice strain on charge/orbital ordering and phase separation in Pr0.7(Ca0.6Sr0.4)0.3MnO3 thin films J. Appl. Phys. 115, 17D708 (2014); 10.1063/1.4863383 Temperature dependence of nanometer-size metallic phase texture and its correlation with bulk magnetic and transport properties and defects of a (La0.4Pr0.6)0.67Ca0.33MnO3 film Appl. Phys. Lett. 101, 022404 (2012); 10.1063/1.4733666 Strain effect caused by substrates on phase separation and transport properties in Pr0.7(Ca0.8Sr0.2)0.3MnO3 thin films J. Appl. Phys. 111, 07D721 (2012); 10.1063/1.3678297 Phase separation and enhanced magnetoresistance in the strained epitaxial La0.625Ca0.375MnO3 (001) films J. Appl. Phys. 111, 066104 (2012); 10.1063/1.3695376 Magneto-and electro-resistance effects in phase separated Pr0.55(Ca0.65S0.35)0.45MnO3 films

We report the fabrication of 0.71Pb(MgNb)O-0.29PbTiO (PMN-0.29PT)-based ferroelectric field effect transistors (FeFETs) by the epitaxial growth of cobalt-doped tin dioxide (SnO) semiconductor thin films on PMN-0.29PT single crystals. Using such FeFETs we realized in situ, reversible, and nonvolatile manipulation of the electron carrier density and achieved a large nonvolatile modulation of the resistance (∼330%) of the SnO:Co films through the polarization switching of PMN-0.29PT at 300 K. Particularly, combining the ferroelectric gating with piezoresponse force microscopy, X-ray diffraction, Hall effect, and magnetoresistance (MR), we rigorously disclose that both sign and magnitude of the MR are intrinsically determined by the electron carrier density, which could modify the s-d exchange interaction of the SnO:Co films. Furthermore, we realized multilevel resistance states of the SnO:Co films by combining the ferroelectric gating with ultraviolet light illumination, demonstrating that the FeFETs have potential applications in multistate resistive memories and electro-optical devices.

With the development of Raman spectroscopy and the expansion of its application domains, conventional methods for spectral data analysis have manifested many limitations. Exploring new approaches to facilitate Raman spectroscopy and analysis has become an area of intensifying focus for research. It has been demonstrated that machine learning techniques can more efficiently extract valuable information from spectral data, creating unprecedented opportunities for analytical science. This paper outlines traditional and more recently developed statistical methods that are commonly used in machine learning (ML) and ML‐algorithms for different Raman spectroscopy‐based classification and recognition applications. The methods include Principal Component Analysis, K‐Nearest Neighbor, Random Forest, and Support Vector Machine, as well as neural network‐based deep learning algorithms such as Artificial Neural Networks, Convolutional Neural Networks, etc. The bulk of the review is dedicated to the research advances in machine learning applied to Raman spectroscopy from several fields, including material science, biomedical applications, food science, and others, which reached impressive levels of analytical accuracy. The combination of Raman spectroscopy and machine learning offers unprecedented opportunities to achieve high throughput and fast identification in many of these application fields. The limitations of current studies are also discussed and perspectives on future research are provided.