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Growth of iron/tungsten disulfide heterostructure films with controlled interface and magnetic properties
The ability to harness excellent magnetic and optical properties within a heterostructure film composed of a magnetic material and a transition metal dichalcogenide (TMD) semiconductor paves a new pathway for the development of multifunctional sensing devices, information storage technology, etc1. Atomically thin tungsten disulfide (WS2) (thickness ≤ 5 nm) has been widely explored as a promising candidate for applications in optoelectronics, spintronics, and valleytronics. The valleytronic property of WS2 can be enhanced when interfacing it with another magnetic material such as iron (Fe), due to the magnetic proximity effect2. However, the growth of this 2D-TMD with controllable thickness, using chemical vapor deposition (CVD), and transferring it onto another substrate (Fe) via a commonly used wet transfer process have remained a challenging task. To overcome this, we employ a combination of pulsed laser deposition (PLD) and sputtering (SP) techniques to grow Fe/WS2 heterostructure films with a controlled interface and desirable magnetic/optical properties. A 5nm thick WS2 film was first grown on MgO substrate using PLD, and a 5nm thick Fe film was then deposited on WS2/MgO using SP. A 2nm thick Ta layer was sputtered on the Fe surface to protect the film from oxidization. X-ray diffraction, Raman and Photoluminescence spectroscopy, and atomic force microscopy confirmed the structure of the heterostructure and the quality of the Fe/WS2 interface. Vibrating sample magnetometry, magneto-optical Kerr effect (MOKE), and magnetic force microscopy indicated that the excellent magnetic properties of Fe are preserved in the Ta/Fe/WS2/MgO heterostructure relative to the Ta/Fe/MgO reference film. MOKE showed a sharp, square magnetic hysteresis loop of Ta/Fe/WS2/MgO with a coercive field (Hc ~ 25 Oe) similar to that of the reference film, Ta/Fe/MgO (Hc ~ 23 Oe). The combined excellent magnetic and optical properties make the Ta/Fe/WS2/MgO heterostructure a promising candidate for a wide range of applications in spintronics, valleytronics, and opto-spincaloritronics3. Our study provides a new, efficient method for the growth of novel 2D van der Waals TMD-based heterostructures with controlled interface properties.
