Via Method for Lithography Free Contact and Preservation of 2D Materials

Abstract

Atomically thin 2D materials span the common components of electronic circuits as metals, semiconductors, and insulators, and can manifest correlated phases such as superconductivity, charge density waves, and magnetism. An ongoing challenge in the field is to incorporate these 2D materials into multilayer heterostructures with robust electrical contacts while preventing disorder and degradation. In particular, preserving and studying air-sensitive 2D materials has presented a significant challenge since they readily oxidize under atmospheric conditions. We report a new technique for contacting 2D materials, in which metal via contacts are integrated into flakes of insulating hexagonal boron nitride, and then placed onto the desired conducting 2D layer, avoiding direct lithographic patterning onto the 2D conductor. The metal contacts are planar with the bottom surface of the boron nitride and form robust contacts to multiple 2D materials. These structures protect air-sensitive 2D materials for months with no degradation in performance. This via contact technique will provide the capability to produce "atomic printed circuit boards" that can form the basis of more complex multilayer heterostructures.

A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics

“…To take advantage of the intrinsically passivated surfaces of TMDs, gentle fabrication techniques are needed to form metal contacts without damaging the underlying semiconductor. A number of new contact techniques have been presented recently, including 1D edge contacts ( 9 ), via contacts embedded in hBN ( 10 ), slowly deposited In/Au contacts ( 11 ), and 2D metals ( 12 ). Recently, Liu et al ( 13 ) have shown that transferring rather than evaporating metal contacts onto TMDs can yield interfaces with no Fermi-level pinning, where the Schottky barrier height can be predicted by the ideal Schottky-Mott rule.…”

Recent progress in contact, mobility, and encapsulation engineering of InSe and GaSe

“…[7][8][9] Today, the 2D family has expanded to comprise inorganic, [9][10][11] organic, 12 and even hybrid organic-inorganic materials. [13][14][15] Extensive research is being carried out to characterize various 2D materials, each offering a unique set of intrinsic properties and covering a wide range of applications, for example, semimetals (graphene), 16 semiconductors (MoS 2 , InSe, and black phosphorus [BP]) 9,10,[17][18][19] ; dielectrics (hexagonal boron nitride [hBN]) 20 ; superconductors (NbSe 2 ) 21,22 ; and topological insulators (Bi 2 Se 3 ). 23 For applications in electronics and optoelectronics, including transistors, photodetectors, photovoltaics, sensors, and light-emitting diodes, semiconducting 2D materials with a finite bandgap, excellent transport properties, and mechanical flexibility are required.…”

Sensitivity of the superconducting state in thin films

“…1a,b), known for its high level of disorder reflected by high R N ( h 4e 2 6.4 kΩ).The second system we investigated is made of sheets exfoliated from a single-crystal of 2H-NbSe 2 (Fig. 1c,d), which are of high purity and are characterized by low R N (< 100 Ω) [30]. Within the field of thin-film superconductors these two systems represent opposite limits with respect to structure and disorder.…”