Band-gap tuning at the strong quantum confinement regime in magnetic semiconductor EuS thin films

Poulopoulos, P.; Lewitz, Björn; Straub, Andreas; Pappas, S. D.; Droulias, Sotirios A.; Baskoutas, Sotirios; Fumagalli, P.

doi:10.1063/1.4720167

Cited by 28 publications

(17 citation statements)

References 26 publications

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“…EuS thin films with a thickness of 25 nm are largely transparent in the visible region, although the UV-Vis spectra show a broad absorption band between 1.8 and 2.8 eV, caused by the transition from the 4f 7 ground state to the 4f 6 5d configuration in Eu 2+ (Figure 2a). This is in line with EuS being a natural ferromagnetic semiconductor [22], showing an optical band gap of 1.65 eV for thin film EuS [23]. EuS thin films with a thickness of 25 nm deposited at 250 °C on Si (100) wafer show a good crystallinity with preferential growth orientation of the (200) planes parallel to the substrate.…”

Section: Resultssupporting

confidence: 72%

SmS/EuS/SmS Tri-Layer Thin Films: The Role of Diffusion in the Pressure Triggered Semiconductor-Metal Transition

2019

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While SmS thin films show an irreversible semiconductor-metal transition upon application of pressure, the switching characteristics can be modified by alloying with other elements, such as europium. This manuscript reports on the resistance response of tri-layer SmS/EuS/SmS thin films upon applying pressure and on the correlation between the resistance response and the interdiffusion between the layers. SmS thin films were deposited by e-beam sublimation of Sm in an H2S atmosphere, while EuS was directly sublimated by e-beam from EuS. Structural properties of the separate thin films were first studied before the deposition of the final nanocomposite tri-layer system. Piezoresistance measurements demonstrated two sharp resistance drops. The first drop, at lower pressure, corresponds to the switching characteristic of SmS. The second drop, at higher pressure, is attributed to EuS, partially mixed with SmS. This behavior provides either a well-defined three or two states system, depending on the degree of mixing. Depth profiling using x-ray photoelectron spectroscopy (XPS) revealed partial diffusion between the compounds upon deposition at a substrate temperature of 400 °C. Thinner tri-layer systems were also deposited to provide more interdiffusion. A higher EuS concentration led to a continuous transition as a function of pressure. This study shows that EuS-modified SmS thin films are possible systems for piezo-electronic devices, such as memory devices, RF (radio frequency) switches and piezoresistive sensors.

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Section: Resultssupporting

confidence: 72%

SmS/EuS/SmS Tri-Layer Thin Films: The Role of Diffusion in the Pressure Triggered Semiconductor-Metal Transition

2019

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“…65 85 Fig. 6 depicts the relation between the absorbance and wavelength , it can be seen that there is a shift in the absorption edge toward shorter wavelengths ( blue shift) this blue shift can be attributed to the quantum confinement [26,27]. It has believed that the absorbance is molarity dependence.…”

Section: Resultsmentioning

confidence: 99%

Molar Concentration Effects on the Optical and Structural Properties of Nanostructural SnO<sub>2</sub> Thin Films

Habubi

Abood

Algamel

2016

ILCPA

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Thin films of nanostructured SnO 2 with different molarites were prepared by chemical spray pyrolysis technique. XRD analysis reveals that all the films were tetragonal polycrystalline with a preferred orientation along (110) plane. AFM measurements indicate that the value of the grain size for 0.05 M, 0.1 M and 0.15 M were 111nm, 78 nm and 58 nm respectively. SEM micrograph proved the existence of small cracks on the film surface, EDS confirmed the composition percentage ratio of Sn and O 2 and no trace of impurities could be detected. PL spectra gives the indication about optical energy gap and the effect of concentration on it which appeared as a blue shift. The transmittance was studied for the deposited thin films ,identifying that the transmittance decreases by the increase in molarity. The value of the optical energy gap of the deposited thin films was increased upon increasing molar concentration due o quantum confinement effect. The Urbach energy was also studied, their values decrease as the molar concentration increase.

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“…This observation renders EuS layers thinner than about 2 nm in 3 d metal/EuS trilayers and multilayers useful for R.T. spintronic applications. Moreover, since EuS is a semiconductor with a direct band gap at about 1.65 eV, combination of magnetic properties at R.T. with band gap tuning due to quantum confinement, which we have recently demonstrated, may merge spintronics and optoelectronics, as for example in spin-controlled light emitting diodes or vertical-cavity surface-emitting lasers11.…”

mentioning

confidence: 95%

Direct evidence for significant spin-polarization of EuS in Co/EuS multilayers at room temperature

Pappas

Poulopoulos

Lewitz

et al. 2013

Sci Rep

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The new era of spintronics promises the development of nanodevices, where the electron spin will be used to store information and charge currents will be replaced by spin currents. For this, ferromagnetic semiconductors at room temperature are needed. We report on significant room-temperature spin polarization of EuS in Co/EuS multilayers recorded by x-ray magnetic circular dichroism (XMCD). The films were found to contain a mixture of divalent and trivalent europium, but only Eu++ is responsible for the ferromagnetic behavior of EuS. The magnetic XMCD signal of Eu at room temperature could unambiguously be assigned to magnetic ordering of EuS and was found to be only one order of magnitude smaller than that at 2.5 K. The room temperature magnetic moment of EuS is as large as the one of bulk ferromagnetic Ni. Our findings pave the path for fabrication of room–temperature spintronic devices using spin polarized EuS layers.

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Band-gap tuning at the strong quantum confinement regime in magnetic semiconductor EuS thin films

Cited by 28 publications

References 26 publications

SmS/EuS/SmS Tri-Layer Thin Films: The Role of Diffusion in the Pressure Triggered Semiconductor-Metal Transition

SmS/EuS/SmS Tri-Layer Thin Films: The Role of Diffusion in the Pressure Triggered Semiconductor-Metal Transition

Molar Concentration Effects on the Optical and Structural Properties of Nanostructural SnO<sub>2</sub> Thin Films

Direct evidence for significant spin-polarization of EuS in Co/EuS multilayers at room temperature

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