Direct Observation of Semiconductor-Metal Phase Transition in Bilayer Tungsten Diselenide Induced by Potassium Surface Functionalization.

Title Direct Observation of Semiconductor-Metal Phase Transition in Bilayer Tungsten Diselenide Induced by Potassium Surface Functionalization.
Authors B. Lei; Y. Pan; Z. Hu; J. Zhang; D. Xiang; Y. Zheng; R. Guo; C. Han; L. Wang; J. Lu; L. Yang; W. Chen
Journal ACS Nano
DOI 10.1021/acsnano.8b00398
Abstract

Structures determine properties of materials and controllable phase transitions are, therefore, highly desirable for exploring exotic physics and fabricating devices. We report a direct observation of a controllable semiconductor-metal phase transition in bilayer tungsten diselenide (WSe2) with potassium (K) surface functionalization. Through the integration of in-situ field-effect-transistor (FET), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy measurements and first-principles calculations, we identify that the electron doping from K adatoms drives bilayer WSe2 from a 2H-phase semiconductor to a 1T'-phase metal. The phase-transition mechanism is satisfactorily explained by the electronic structures and energy alignment of the 2H and 1T' phases. This explanation can be generally applied to understand doping induced phase transitions in two-dimensional (2D) structures. Finally, the associated dramatic changes of electronic structures and electrical conductance make this controllable semiconductor-metal phase transition of interest for 2D semiconductors based electronic and optoelectronic devices.

Citation B. Lei; Y. Pan; Z. Hu; J. Zhang; D. Xiang; Y. Zheng; R. Guo; C. Han; L. Wang; J. Lu; L. Yang; W. Chen.Direct Observation of Semiconductor-Metal Phase Transition in Bilayer Tungsten Diselenide Induced by Potassium Surface Functionalization.. ACS Nano. 2018. doi:10.1021/acsnano.8b00398

Related Elements

Potassium

Elemental PotassiumSee more Potassium products. Potassium (atomic symbol: K, atomic number: 19) is a Block S, Group 1, Period 4 element with an atomic weight of 39.0983. The number of electrons in each of Potassium's shells is [2, 8, 8, 1] and its electron configuration is [Ar] 4s1. The potassium atom has a radius of 227.2 pm and a Van der Waals radius of 275 pm. Potassium was discovered and first isolated by Sir Humphrey Davy in 1807. Potassium is the seventh most abundant element on earth. It is one of the most reactive and electropositive of all metals and rapidly oxidizes. As with other alkali metals, potassium decomposes in water with the evolution of hydrogen because of its reacts violently with water, it only occurs in nature in ionic salts.Potassium Bohr Model In its elemental form, potassium has a silvery gray metallic appearance, but its compounds (such as potassium hydroxide) are more frequently used in industrial and chemical applications. The origin of the element's name comes from the English word 'potash,' meaning pot ashes, and the Arabic word qali, which means alkali. The symbol K originates from the Latin word kalium.

Selenium

Selenium Bohr ModelSee more Selenium products. Selenium (atomic symbol: Se, atomic number: 34) is a Block P, Group 16, Period 4 element with an atomic radius of 78.96. The number of electrons in each of Selenium's shells is 2, 8, 18, 6 and its electron configuration is [Ar] 3d10 4s2 4p4. The selenium atom has a radius of 120 pm and a Van der Waals radius of 190 pm. Selenium is a non-metal with several allotropes: a black, vitreous form with an irregular crystal structure three red-colored forms with monoclinic crystal structures and a gray form with a hexagonal crystal structure, the most stable and dense form of the element. Elemental SeleniumOne of the most common uses for selenium is in glass production the red tint that it lends to glass neutralizes green or yellow tints from impurities in the glass materials. Selenium was discovered and first isolated by Jöns Jakob Berzelius and Johann Gottlieb Gahn in 1817. The origin of the name Selenium comes from the Greek word "Selênê," meaning moon.

Tungsten

See more Tungsten products. Tungsten (atomic symbol: W, atomic number: 74) is a Block D, Group 6, Period 6 element with an atomic weight of 183.84. The number of electrons in each of tungsten's shells is [2, 8, 18, 32, 12, 2] and its electron configuration is [Xe] 4f14 5d4 6s2. Tungsten Bohr ModelThe tungsten atom has a radius of 139 pm and a Van der Waals radius of 210 pm. Tungsten was discovered by Torbern Bergman in 1781 and first isolated by Juan José Elhuyar and Fausto Elhuyar in 1783. In its elemental form, tungsten has a grayish white, lustrous appearance. Elemental TungstenTungsten has the highest melting point of all the metallic elements and a density comparable to that or uranium or gold and about 1.7 times that of lead. Tungsten alloys are often used to make filaments and targets of x-ray tubes. It is found in the minerals scheelite (CaWO4) and wolframite [(Fe,Mn)WO4]. In reference to its density, Tungsten gets its name from the Swedish words tung and sten, meaning heavy stone.

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