以化學氣相沉積法合成具有雙極電性的二硒化錸晶體並應用於近紅外光發光二極體

Abstract

過渡金屬二硫族化物(TMDs)其獨特的光與電的性質引起研究的熱潮。二硒化錸（ReSe2）屬於過渡金屬二硫族化物的新成員，具有低對稱性的扭曲三斜晶系結構，它是一種層狀的半導體材料，能隙介於1.1~1.3 eV之間，能隙大小不會隨著單層到塊材的變化而有大幅的變動，是近紅外光發光材料的理想選擇。更重要的是，二硒化錸本身具有雙極場效應的性質，適合發展單一材料的發光電晶體(light emitting transistor, LET)。在目前的發光二極體（LED）的發展中，用於發光二極體的材料通常具有寬的放光範圍但結晶度較低，然而，有關於過渡金屬二硫族化物所製成的二極體中，其材料包括二硫化鉬、二硒化鎢和黑磷，具有高結晶性且較低的驅動電壓，並且可利用閘極調控雙極的場效應性質，但其雙極電性可能會受到厚度的影響而改變，成為在光電元件應用中主要的問題。 為了解決這個問題，我們發展出單一材料的發光電晶體，利用二硒化錸材料作為發光層並藉由不對稱電極來製作近紅外光發光電晶體，在本研究中，我們採用化學氣相沉積法合成大面積且具有雙極電性的二硒化錸薄膜，並使用拉曼、光致螢光光譜、X射線光電子能譜、能量色散光譜以及高解析穿透式電子顯微鏡來鑑定我們合成出的二硒化錸的結構及元素組成，對於二硒化錸電晶體的電性量測結果為雙極性傳輸，此一特性代表其電晶體可進一步應用於近紅外光發光的應用。

Transition metal dichalcogenides (TMDs) with their unique optical and electrical properties have reinvigorated the optoelectronics research field. Rhenium diselenide (ReSe2) belongs to a new member of the TMD family and has a distorted triclinic crystal structure of low symmetry. ReSe2 is a layered semiconductor with a direct bandgap of 1.1~1.3 eV, which is nearly layer-independent from bulk to monolayer and ideal for a near-infrared emitting material. More importantly, ReSe2 exhibits inherent ambipolar field-effect nature and can be employed for a single-component light-emitting transistor (LET). In the current development of light-emitting diodes (LEDs), the materials used for LED are generally with a wide emission range but of low crystallinity. Nevertheless, in the recent reports of TMD-based LEDs, the constituent materials (such as MoS2, WSe2, and black phosphorus) are of high crystallinity with low potential barrier and have gate tunable ambipolar field-effect behavior, but their layer-dependent ambipolar nature have become a major concern in optoelectronic applications. To address this issue, we developed a single-component LET by utilizing ReSe2 as the emission layer together with asymmetric electrodes to build up a near-infrared LET. Here, we report the large-domain synthesis of ambipolar ReSe2 crystal with a chemical-vapor-deposition (CVD) technique. The as-synthesized ReSe2 crystals were studied by Raman, photoluminescence, X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM) to show their structural and compositional characteristics. The electrical measurements of the as-fabricated ReSe2-LET have showed the ambipolar characteristics of the devices, which will further be used for developing a near-infrared LED.