Fermi Level Tuning by Low Temperature Atomic Layer Deposition/Epitaxy (ALD/ALE) of Ternary Chalcogenide Layers

通过三元硫族化物层的低温原子层沉积/外延 (ALD/ALE) 调节费米能级

• 批准号: 237711259
• 负责人: Professor Dr. Stephan Schulz
• 金额: --
• 依托单位: Institut für Metallische Werkstoffe
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/237711259?language=en
• 关键词: Fermi; Level; Tuning; Low; Temperature

Atomic Layer Deposition(A LD) is the synthesis technique of choice for the deposition of telluride based ternary chalcogenide layers. Three chalcogenide systems,( Sb1-xBix)2Te3, (Ge Te)1-x(Sb2Te3)x and (GeTe)1-x(Bi2Te3)x) will be investigated for which the composition factor x will be optimized in order to level the Fermi energy in the Dirac cone, thus achieving a low carrier concentration and a zero Seebeck coefficient. For the latter physical quantity a Hall-Seebeck measurement platform with the additional capability for tuning the Fermi energy level by applying electric field will be utilized. The ternary layers will be synthesized by ALD processes on suitable amorphous and single-crystalline substrates at rather low temperatures (RT to 150'C). We will study the substrate influence (amorphous silica versus single-crystalline substrates like e .g. GaAs and BaF2) on the layer morphology band structure and topologic transport properties. For the suppression of antisite defects, the annealing under tellurium vapor is integrated in the synthesis procedure, although the ideal stoichiometric composition is achieved by the low-T A LD processes as well as the use of suitable (reactive) metal organic precursors. For achieving ideal ALD processes, the development and testing of specific volatile but thermally stable (storable) metal-organic precursors is one essential project goal, which will be addressed by the Schulz group from Essen for binary compounds such as Bi2Te3, Sb2Te3 and GeTe. Silyl- substituted telluranes of the general type (R3Si)2Te (R = Me, Et, i-Pr, Ph, …) are synthesized, which readily react with either antimony and bismuth alkoxides of the type M(OR')x and amides M(NR'2)x, (M = Sb, Bi; x = 3; M = Ge, x = 2; R' = Me, E t , n-Pr, n-Bu, i-Pr , i-Bu, t-Bu) with subsequent elimination of silylamides R3SiNR'2 or silylethers R3SiOR' due to the formation of thermodynamically stable Si-N or Si-O bonds. Variation of the organic substituents R and R' allows the fine-tuning of the thermal stability, hence the suitability for decomposition-free storage( R, R' = Me, Et, n-Pr, i-Pr). Moreover, the vapor and sublimation pressure (volatility) as well as reactivity of the compound significantly depends on the steric size of the organic group (kinetic stabilization). Based on the optimized ALD processes for binary semi-conductors the Nielsch group from Hamburg will optimize the topological properties of ternary systems by alternating applications of binary processes and carry out all major physical characterization (mentioned above).

原子层沉积（ALD）是用于沉积碲化物基三元硫属化物层的选择的合成技术。 三个硫族化合物系统，（Sb_（1-x）Bix）_2 Te_3，（Ge_Te）_（1-x）（Sb_2 Te_3）_x和（Ge_Te）_（1-x）（Bi_2 Te_3）_x）将被研究，其中的组成因子x将被优化，以使狄拉克锥中的费米能水平化，从而实现低载流子浓度和零塞贝克系数。对于后一个物理量，将利用具有通过施加电场来调谐费米能级的附加能力的霍尔-塞贝克测量平台。三元层将通过ALD工艺在相当低的温度（RT至150 ℃）下在合适的非晶和单晶衬底上合成。我们将研究基板的影响（无定形二氧化硅与单晶基板，如GaAs和BaF_2）对薄膜形貌、能带结构和拓扑输运性质的影响。为了抑制反位缺陷，碲蒸气下的退火被集成在合成过程中，虽然理想的化学计量组成是通过低T A LD工艺以及使用合适的（反应性）金属有机前体来实现的。为了实现理想的ALD工艺，开发和测试特定的挥发性但热稳定（可储存）的金属有机前体是一个重要的项目目标，这将由埃森的Schulz小组针对二元化合物（如Bi 2 Te 3，Sb 2 Te 3和GeTe）进行解决。一般类型（R3 Si）2 Te的甲硅烷基取代的碲烷（R = Me，Et，i-Pr，Ph，...），其易于与M（OR ′）x型锑和铋醇盐和酰胺M（NR ′ 2）x反应，（M = Sb，Bi; x = 3; M = Ge，x = 2; R' = Me，Et，n-Pr，n-Bu，i-Pr，i-Bu，t-Bu），随后由于形成化学稳定的Si-N或Si-O键而消除甲硅烷基酰胺R3 SiNR' 2或甲硅烷基醚R3 SiOR '。有机取代基R和R'的变化允许微调热稳定性，因此适合于无分解储存（R，R' = Me，Et，n-Pr，i-Pr）。此外，化合物的蒸气压和升华压（挥发性）以及反应性显著取决于有机基团的空间尺寸（动力学稳定性）。基于二元半导体的优化ALD工艺，汉堡的Nielsch集团将通过交替应用二元工艺来优化三元系统的拓扑特性，并进行所有主要的物理表征（如上所述）。