MBE-grown ultrathin PtTe<sub>2</sub> films and their layer-dependent electronic structures

Zhang, Lei; Yang, Tong; Arramel, Arramel; Feng, Yuan Ping; Wee, Andrew Thye Shen; Wang, Zhuo

doi:10.1039/d2nr00944g

Cited by 9 publications

(9 citation statements)

References 40 publications

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“…PtTe 2 was grown by molecular beam epitaxy. This approach has been shown by several groups to result in high quality PtTe 2 films down to monolayer thickness if grown at low (250 °C) temperatures. , Growth at temperatures above 300 °C favors formation of bilayer thick islands Figure shows the as grown PtTe 2 film, that consists of both mono- and bilayer islands.…”

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confidence: 98%

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Lasek

Ghorbani‐Asl

et al. 2022

Nano Lett.

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Monolayer PtTe2 is a narrow gap semiconductor while Pt2Te2 is a metal. Here we show that the former can be transformed into the latter by reaction with vapor-deposited Pt atoms. The transformation occurs by nucleating the Pt2Te2 phase within PtTe2 islands, so that a metal–semiconductor junction is formed. A flat band structure is found with the Fermi level of the metal aligning with that of the intrinsically p-doped PtTe2. This is achieved by an interface dipole that accommodates the ∼0.2 eV shift in the work functions of the two materials. First-principles calculations indicate that the origin of the interface dipole is the atomic scale charge redistributions at the heterojunction. The demonstrated compositional phase transformation of a 2D semiconductor into a 2D metal is a promising approach for making in-plane metal contacts that are required for efficient charge injection and is of particular interest for semiconductors with large spin–orbit coupling, like PtTe2.

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confidence: 98%

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Lasek

Ghorbani‐Asl

et al. 2022

Nano Lett.

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“…Figures d–f present the optical microscopy, scanning electron microscopy, and atomic force microscopy images of as-grown PtTe 2 single crystals in regular hexagonal geometry, respectively. The Raman spectrum (see Figure g) acquired from the representative as-grown PtTe 2 nanoflakes shows two characteristic modes centered at 114.2 and 157.4 cm –1 , which are assigned to the E g and A 1g modes of PtTe 2 , respectively. , Moreover, to confirm the chemical compositions of the sample, we conducted EDS elemental analysis and mappings characterizations, as shown in Figure S1. The results confirm the synthesis of PtTe 2 in the stoichiometric ratio.…”

Section: Resultsmentioning

confidence: 99%

“…The interlayer separation (see Figure b) between MoS 2 and bilayer PtTe 2 (i.e., bulk material) is calculated to be 3.2 Å, which is smaller than that of MoS 2 –graphene (3.4 Å). The small interlayer spacing between MoS 2 and bilayer PtTe 2 leads to covalent-like ultrastrong forces benefiting from the strong thickness-dependent nature of PtTe 2 . ,, It is reported that PtTe 2 layers would evolve from semiconductive to metallic as the thickness increases owing to strong interlayer interactions, which provides complementary proof to our claim . The differential charge density for the MoS 2 /PtTe 2 heterostructure (see Figure c) displays obvious charge redistribution at the interfacial layer, further indicating strong interlayer coupling between MoS 2 and PtTe 2 .…”

Section: Resultsmentioning

confidence: 99%

“…The Raman spectrum (see Figure 2g) acquired from the representative as-grown PtTe 2 nanoflakes shows two characteristic modes centered at 114.2 and 157.4 cm −1 , which are assigned to the E g and A 1g modes of PtTe 2 , respectively. 32,40 Moreover, to confirm the chemical compositions of the sample, we conducted EDS elemental analysis and mappings characterizations, as shown in Figure S1.…”

Section: Resultsmentioning

confidence: 99%

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Improving Contacts and Electrical Performances of Nanofilms of MoS₂ Transistors through Ultrastrong vdW Integration with Dirac Semimetal PtTe₂

Hao

Han

Zhang

et al. 2023

ACS Appl. Nano Mater.

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Semiconductor−metal contacts as one major challenge have severely hindered the further progress of two-dimensional (2D) electronics.Here, we present a simple and effective strategy to improve the contacts and electrical performances by fabricating van der Waals (vdW) heterostructures with 2D semiconductor MoS 2 and type-II Dirac semimetal PtTe 2 . The semiconductor MoS 2 and Dirac semimetal PtTe 2 nanoflakes are synthesized through CVD routes separately, followed by systematic material characterizations to confirm their structures. Furthermore, we constructed MoS 2 / PtTe 2 vdW heterostructures via a transfer technology with as-grown MoS 2 and PtTe 2 nanoflakes. The field-effect transistor based on MoS 2 /PtTe 2 heterostructures shows ohmic contact and improved electrical performances, such as two-terminal carrier mobility (∼38.2 cm 2 •V −1 •s −1 ) and ON/OFF ratio (∼10 4 ). We ascribe the improvement of contact and electrical performances to the utilization of ultrahigh-conductive layered PtTe 2 as an interlayer. The theoretical calculations demonstrate that the vdW contact can eliminate the Fermi level pinning effect; meanwhile, the ultrastrong covalent-like interlayer coupling guarantees the high-efficiency carrier injection across PtTe 2 and MoS 2 . The concept that synergizes 2D semiconductors as the channel and Dirac semimetal PtTe 2 as an interlayer will offer a promising approach toward the design of high-performance 2D electronics.

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“…Specifically, the Pt-tellurides have many attractive attributes that allow us to gain better fundamental understanding of van der Waals (vdW) materials and their potential applications. The Pt-tellurides have attracted interest for: (i) layer-dependent electronic properties that cause opening of a band gap in monolayer PtTe 2 , while the system otherwise is (semi)metallic, − (ii) topological features , for both PtTe 2 and Pt 3 Te 4 and a strong spin texture that unlike the topological states persist down to the monolayer, making them potentially interesting materials for spintronics applications, , and (iii) useful electrochemical properties for hydrogen evolution as well as oxygen reduction reactions. − …”

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confidence: 99%

Controlling Stoichiometry in Ultrathin van der Waals Films: PtTe₂, Pt₂Te₃, Pt₃Te₄, and Pt₂Te₂

et al. 2022

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The platinum−tellurium phase diagram exhibits various (meta)stable van der Waals (vdW) materials that can be constructed by stacking PtTe 2 and Pt 2 Te 2 layers. Monophase PtTe 2 , being the thermodynamically most stable compound, can readily be grown as thin films. Obtaining the other phases (Pt 2 Te 3 , Pt 3 Te 4 , Pt 2 Te 2 ), especially in their ultimate thin form, is significantly more challenging. We show that PtTe 2 thin films can be transformed by vacuum annealing-induced Te-loss into Pt 3 Te 4 -and Pt 2 Te 2 -bilayers. These transformations are characterized by scanning tunneling microscopy and X-ray and angle resolved photoemission spectroscopy. Once Pt 3 Te 4 is formed, it is thermally stable up to 350°C. To transform Pt 3 Te 4 into Pt 2 Te 2 , a higher annealing temperature of 400°C is required. The experiments combined with density functional theory calculations provide insights into these transformation mechanisms and show that a combination of the thermodynamic preference of Pt 3 Te 4 over a phase segregation into PtTe 2 and Pt 2 Te 2 and an increase in the Te-vacancy formation energy for Pt 3 Te 4 compared to the starting PtTe 2 material is critical to stabilize the Pt 3 Te 4 bilayer. To desorb more tellurium from Pt 3 Te 4 and transform the material into Pt 2 Te 2 , a higher Te-vacancy formation energy has to be overcome by raising the temperature. Interestingly, bilayer Pt 2 Te 2 can be retellurized by exposure to Te-vapor. This causes the selective transformation of the topmost Pt 2 Te 2 layer into two layers of PtTe 2 , and consequently the synthesis of e Pt 2 Te 3 . Thus, all known Pt-telluride vdW compounds can be obtained in their ultrathin form by carefully controlling the stoichiometry of the material.

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MBE-grown ultrathin PtTe₂ films and their layer-dependent electronic structures

Abstract: Two-dimensional (2D) platinum ditelluride (PtTe2) has received significant attention for 2D photodetector applications due to its novel physical properties. One of the critical factors that affect device performance is the...

Cited by 9 publications

References 40 publications

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Improving Contacts and Electrical Performances of Nanofilms of MoS₂ Transistors through Ultrastrong vdW Integration with Dirac Semimetal PtTe₂

Controlling Stoichiometry in Ultrathin van der Waals Films: PtTe₂, Pt₂Te₃, Pt₃Te₄, and Pt₂Te₂

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MBE-grown ultrathin PtTe2 films and their layer-dependent electronic structures

Abstract: Two-dimensional (2D) platinum ditelluride (PtTe2) has received significant attention for 2D photodetector applications due to its novel physical properties. One of the critical factors that affect device performance is the...

Cited by 9 publications

References 40 publications

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe2 to Pt2Te2

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe2 to Pt2Te2

Improving Contacts and Electrical Performances of Nanofilms of MoS2 Transistors through Ultrastrong vdW Integration with Dirac Semimetal PtTe2

Controlling Stoichiometry in Ultrathin van der Waals Films: PtTe2, Pt2Te3, Pt3Te4, and Pt2Te2

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MBE-grown ultrathin PtTe₂ films and their layer-dependent electronic structures

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Formation of In-Plane Semiconductor–Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Improving Contacts and Electrical Performances of Nanofilms of MoS₂ Transistors through Ultrastrong vdW Integration with Dirac Semimetal PtTe₂

Controlling Stoichiometry in Ultrathin van der Waals Films: PtTe₂, Pt₂Te₃, Pt₃Te₄, and Pt₂Te₂