Two-dimensional (2D) palladium diselenide (PdSe₂) layers are projected to exhibit a number of intriguing electrical properties such as semiconducting-to-metallic transitions. Precisely modulating their morphology and chemistry is essential for realizing such opportunities, which is particularly demanded on a large dimension under flexible processing conditions toward broadening their practical device applicability. Herein, we explore a wafer-scale growth of 2D PdSe₂ layers and introduce semiconducting-to-metallic transitions into them at as low as 330 °C, a temperature compatible with a range of polymeric substrates as well as the back-end-of-line (BEOL) processes. Two independent physical and chemical approaches of thickness modulation and anion exchange are demonstrated to induce the low-temperature-driven electrical transitions. Wafer-scale 2D PdSe₂ layers grown from a scalable selenization of thin (∼2 nm) Pd exhibit p-type semiconducting characteristics, which completely vanish with increasing thickness. Furthermore, a postgrowth reaction involving an exchange of selenium (Se)-to-tellurium (Te) ions chemically introduces the semiconducting-to-metallic transitions through the conversion of PdSe₂-to-palladium ditelluride (PdTe₂). A significant reduction of the bandgap energy from 0.7 to 0 V is observed to be associated with the transitions, while the converted 2D layers remain to be highly metallic irrespective of thickness variations. These controlled transition characteristics are employed to fabricate “all-2D” flexible devices employing semiconducting 2D layer channels and metallic 2D layer electrodes on a wafer-scale.

中文翻译：

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通过低温阴离子交换和厚度调制将半导体-金属转变引入晶圆级 2D PdSe2 层


二维 （2D） 二硒化钯 （PdSe₂） 层被预测表现出许多有趣的电特性，例如半导体到金属的转变。精确调节它们的形态和化学性质对于实现此类机会至关重要，这在灵活的加工条件下对大尺寸尤其要求，以扩大其实际器件的适用性。在本文中，我们探索了 2D PdSe₂ 层的晶圆级生长，并在低至 330 °C 的温度下引入半导体到金属的转变，该温度与一系列聚合物衬底以及后端 （BEOL） 工艺兼容。证明了厚度调制和阴离子交换的两种独立的物理和化学方法可诱导低温驱动的电转变。从薄 （∼2 nm） Pd 的可扩展硒化生长的晶圆级 2D PdSe₂ 层表现出 p 型半导体特性，随着厚度的增加而完全消失。此外，涉及硒 （Se） 到碲 （Te） 离子交换的生长后反应通过 PdSe₂ 转化为二碲化钯 （PdTe₂） 以化学方式引入半导体到金属的转变。观察到带隙能量从 0.7 V 显著降低到 0 V 与跃迁有关，而无论厚度变化如何，转换后的 2D 层仍然是高度金属化的。这些受控的转变特性被用来制造“全 2D”柔性器件，采用晶圆级的半导体 2D 层通道和金属 2D 层电极。