Formation of an MoTe<sub>2</sub> based Schottky junction employing ultra-low and high resistive metal contacts

Aftab, Sikandar; Iqbal, Muhammad Waqas; Afzal, Amir Muhammad; Khan, Muhammad Farooq; Hussain, Ghulam; Waheed, Hafiza Sumaira; Kamran, Muhammad Arshad

doi:10.1039/c8ra09656b

Cited by 31 publications

(44 citation statements)

References 42 publications

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“…According to energy band diagram of the bulk MoS 2 and Cr contacts (Figure 10b), the electron affinity of MoS 2 is ∼4.0 eV, 43 and the Cr work function is equal to ∼4.5 eV, which results in a low Schottky barrier under equilibrium condition. 44 Under laser illumination and biasing voltage, electron/hole pairs are generated in the thinned MoS 2 and extracted from the channel 43 (Figure 10c). Current–voltage characteristics ( I – V ) of the device are investigated in dark and under 532 nm laser illumination with 2.20 μW incident power before and after plasma etching process.…”

Section: Thinned Mos2 Flake Photodetectormentioning

confidence: 99%

Controlled Plasma Thinning of Bulk MoS₂ Flakes for Photodetector Fabrication

2019

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The electronic properties of layered materials are directly determined based on their thicknesses. Remarkable progress has been carried out on synthesis of wafer-scale atomically molybdenum disulfide (MoS2) layers as a two-dimensional material in the past few years in order to transform them into commercial products. Although chemical/mechanical exfoliation techniques are used to obtain a high-quality monolayer of MoS2, the lack of suitable control in the thickness and the lateral size of the flakes restrict their benefits. As a result, a straightforward, effective, and reliable approach is widely demanded to achieve a large-area MoS2 flake with control in its thickness for optoelectronic applications. In this study, thick MoS2 flakes are obtained by a short-time bath sonication in dimethylformamide solvent, which are thinned with the aid of a sequential plasma etching process using H2, O2, and SF6 plasma. A comprehensive study has been carried out on MoS2 flakes based on scanning electron microscopy, atomic force microscopy, Raman, transmission electron microscopy, and X-ray photoelectron microscopy measurements, which ultimately leads to a two-cycle plasma thinning method. In this approach, H2 is used in the passivation step in the first subcycle, and O2/SF6 plasma acts as an etching step for removing the MoS2 layers in the second subcycle. Finally, we show that this technique can be enthusiastically used to fabricate MoS2-based photodetectors with a considerable photoresponsivity of 1.39 A/W and a response time of 0.45 s under laser excitation of 532 nm.

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Section: Thinned Mos2 Flake Photodetectormentioning

confidence: 99%

Controlled Plasma Thinning of Bulk MoS₂ Flakes for Photodetector Fabrication

2019

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“…The metal-semiconductor (MS) junction is well known to be a Schottky barrier or ohmic junction based on the corresponding work function of metal compared to the semiconductor and its conductivity type. For the p-type semiconductor, the Schottky barrier is formed when metal work function is smaller than the semiconductor 5,[42][43][44] . SBD formed by Schottky barrier is a widely used component in electronics such as multipliers, microwave mixer and photodetectors, due to its high-frequency capability 45 and strong nonlinear current-voltage characteristics.…”

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confidence: 99%

“…Moreover, it is known that SBDs show promising electronic applications and can be used extensively in power electronics due to the low voltage drop in forward bias. It can also be used as photodiodes, power diodes, sensors, varistors and varactors owing to the nonlinear I-V behavior 5,46 .…”

mentioning

confidence: 99%

“…S1. It has been stated that the metals having lower work function are suitable for p-GeSe to form a facile Schottky barrier height 5,43,44 . It was found that p-GeSe and metal interface could be either an ohmic or rectifying behavior depending on metals and semiconductor working function value.…”

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confidence: 99%

“…It was found that p-GeSe and metal interface could be either an ohmic or rectifying behavior depending on metals and semiconductor working function value. Figure 1c depicts GeSe (Φ ~ 4.83 eV) 47 ,Pd (Φ ~ 5.6 eV) 43 and Cr (Φ ~ 4.5 eV) 5,48 were used as electrode contacts in GeSe flake. Initially, the electrical characteristics of the p-GeSe FETs with Cr/Au and Pd/ Au electrodes were measured.…”

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confidence: 99%

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Asymmetric electrode incorporated 2D GeSe for self-biased and efficient photodetection

Hussain

Aftab

Jaffery

et al. 2020

Sci Rep

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2D layered germanium selenide (GeSe) with p-type conductivity is incorporated with asymmetric contact electrode of chromium/Gold (Cr/Au) and Palladium/Gold (Pd/Au) to design a self-biased, high speed and an efficient photodetector. The photoresponse under photovoltaic effect is investigated for the wavelengths of light (i.e. ~220, ~530 and ~850 nm). The device exhibited promising figures of merit required for efficient photodetection, specifically the Schottky barrier diode is highly sensitive to NIR light irradiation at zero voltage with good reproducibility, which is promising for the emergency application of fire detection and night vision. The high responsivity, detectivity, normalized photocurrent to dark current ratio (NPDR), noise equivalent power (NEP) and response time for illumination of light (~850 nm) are calculated to be 280 mA/W, 4.1 × 10 9 Jones, 3 × 10 7 W −1 , 9.1 × 10 −12 WHz −1/2 and 69 ms respectively. The obtained results suggested that p-GeSe is a novel candidate for SBD optoelectronics-based technologies. Two-dimensional (2D) materials have chronically been the most widely studied materials, particularly after the successful scotch tape test to exfoliate graphene by Andre Geim and Kostya Novoselov in 2004 1. 2D materials possess excellent electrical and mechanical properties toward diverse electronic device applications. Graphene, being the prototype of 2D materials 2,3 , has been studied broadly for its exotic electrical, optical, and mechanical properties 3,4. Besides, the group-IV transition metal dichalcogenides (TMDs) having a bandgap of around 1 to 2 eV 5-7 have attracted increasing interest because of their promising electronic and optoelectronic device applications 3,8-21. Graphene possesses extremely high carrier mobility (>10 5 cm 2 V −1 s −1), but the absence of band gap limits its electronic and optoelectronic applications 22. Therefore, TMDs with the properties of graphene-like stature, bandgap tunability, weak van der Waals-like forces and stability have intrigued the interest of the scientific community. TMDs are the family of 2D materials having the chemical composition of MX 2 , where M stands for the transition metal elements (M = Mo, W, Ta, Ge…etc) and X for the chalcogen elements (X = Se, S and Te). Among TMDs, Ge-based materials are preferred for applications due to their abundance on earth and environmentally friendly nature 23. With Se, the p-type Germanium from a narrow bandgap semiconductor material as p-GeSe having exciting application in near-infrared (NIR) photodetectors and electron tunnelling devices. p-GeSe has an indirect bandgap of 1.08 eV in the bulk 24,25 , and a direct bandgap of ~1.7 eV in monolayers 24,26,27. Few layers of p-GeSe can be obtained from bulk by mechanical exfoliation method 28. Among the many applications, p-GeSe shows tremendous capability in the realm of photovoltaics, because of its excellent optical, material and electrical properties. Therefore, it is well known as substitution of phosphorene 29. Moreover, GeSe is considered as an amb...

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Van der Waals Multi‐Heterostructures (PN, PIN, and NPN) for Dynamic Rectification in 2D Materials

Aftab

Samiya

Haq

et al. 2020

Adv Materials Inter

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Here, van der Waals multi‐heterojunctions (PN, NP, PIN, and NPN) are fabricated by stacking of MoTe2, hexagonal boron nitride (h‐BN), and MoSe2 nanoflakes using a mechanical‐exfoliation technique where the dynamic rectification is examined. Low‐resistance metal contacts Al/Au and Pt/Au are applied to MoSe2 and MoTe2, respectively, and gate‐dependent rectifying behavior is achieved, with a rectification ratio of up to 105 in PN devices. It is found that the performance of the device is enhanced by placing an interfacial layer h‐BN between two opposite layers of 2D materials where the rectification ratio is found to be >106 with the ideality factor ≈1.3 in the PIN devices. Also, using the conventional Richardson's plot, the barrier heights of PN and PIN diodes are calculated to be 260 and 490 meV at zero gate bias, respectively. As well, the devices exhibit good performance with a built‐in electric field observed in both PN and PIN diodes, which gives rise to an open‐circuit voltage (Voc) and short‐circuit current (Isc) under zero external bias. Remarkably, it is found that the performance of the devices also gets better by forming double heterojunction (NPN) layer than PN or NP layers. The device is also tested for a rectification application, and it successfully rectifies an input alternating‐current signal. These findings are important for the development of nano‐ and optoelectronics devices.

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Formation of an MoTe₂ based Schottky junction employing ultra-low and high resistive metal contacts

Abstract: Schottky-barrier diodes have great importance in power management and mobile communication because of their informal device technology, fast response and small capacitance.

Cited by 31 publications

References 42 publications

Controlled Plasma Thinning of Bulk MoS₂ Flakes for Photodetector Fabrication

Controlled Plasma Thinning of Bulk MoS₂ Flakes for Photodetector Fabrication

Asymmetric electrode incorporated 2D GeSe for self-biased and efficient photodetection

Van der Waals Multi‐Heterostructures (PN, PIN, and NPN) for Dynamic Rectification in 2D Materials

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Formation of an MoTe2 based Schottky junction employing ultra-low and high resistive metal contacts

Abstract: Schottky-barrier diodes have great importance in power management and mobile communication because of their informal device technology, fast response and small capacitance.

Cited by 31 publications

References 42 publications

Controlled Plasma Thinning of Bulk MoS2 Flakes for Photodetector Fabrication

Controlled Plasma Thinning of Bulk MoS2 Flakes for Photodetector Fabrication

Asymmetric electrode incorporated 2D GeSe for self-biased and efficient photodetection

Van der Waals Multi‐Heterostructures (PN, PIN, and NPN) for Dynamic Rectification in 2D Materials

Contact Info

Product

Resources

About

Formation of an MoTe₂ based Schottky junction employing ultra-low and high resistive metal contacts

Controlled Plasma Thinning of Bulk MoS₂ Flakes for Photodetector Fabrication

Controlled Plasma Thinning of Bulk MoS₂ Flakes for Photodetector Fabrication