Keynote Talk 

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Dr. Nilanthy Balakrishnan: "Physics and Applications of Indium Selenide Based van der Waals Heterostructures"

 

Keele University, United Kingdom 

The pressing demand for device minaturizaton can be fulfilled by two-dimensional (2D) semiconducting materials. Among the 2D semiconducting materials, indium selenide (InSe) compounds are attracting great attention due to their desirable electronic and optical properties [1-2]. Indium selenide compounds can exist with different stoichiometries (e.g. InSe, In2Se3 and In4Se3) and polytype phases (α, β, γ, etc.), providing band gaps tunable from the near infrared to the visible range (1.2 - 2 eV) of the electromagnetic spectrum [2], a high electron mobility at room temperature (> 0.1 m²/Vs) [1], room temperature ferroelectricity [3] and strong
carrier correlations in atomically thin layers due to an inverted “Mexican hat” valence band [4].

 

Here, we present our recent work on InSe based van der Waals heterostructures of interest for optoelectronics, thermoelectrics and nanoelectronics. Both InSe/GaSe and InSe/In2O3 heterojunctions exhibit room temperature electroluminescence and spectral response from the near-infrared to the visible and near-ultraviolet ranges [5-6]. On the other hand, the nanoscale thermal properties of InSe layers show an anomalous low and
anisotropic thermal conductivity, which is smaller than that of low-κ dielectrics, such as silicon oxide [7]. The thermal response of free-standing InSe layers and layers supported by a substrate, reveals the role of interfacial thermal resistance, phonon scattering, and strain. These thermal properties are critical for future emerging technologies, such as field-effect transistors that require efficient heat dissipation or thermoelectric energy conversion with both low thermal conductance and high electron mobility 2D materials, such as InSe.

 

Furthermore, we report on the ferroelectric semiconductor α-In2Se3 embedded between two single-layer
graphene electrodes. We show how the ferroelectric polarization of the In2Se3 layer can modulate the transmission of electrons across the graphene/In2Se3 interface, leading to memristive effects that can be controlled by wither applied voltages or by light [8].


References


1. Bandurin, D.A., et al., Nat. Nanotechnol.. 12, 223-227 (2017).
2. Huang, W., et al., Cryst. Eng. Comm.. 18, 3968-84 (2016).
3. Zheng, C., et al., Sci. Adv., 4, eaar7720 (2018).
4. Debbichi, L., et al., J Phys Chem Lett, 6, 3098-103 (2015).
5. Balakrishnan, N., et al., Adv. Opt. Mater. 2, 1064 – 9 (2015).
6. Balakrishnan, N., et al., 2D Mater., 4, 025043 (2017).
7. Buckley, D., et al., Adv. Funct. Mater., 31, 2008967 (2020).
8. Xie, S., et al., 2D Mater., 8, 045020 (2021).