用于低温扫描隧道显微镜中原位沉积孤立原子的微型蒸发器
A miniature evaporator for in-operando deposition of isolated atoms in a low-temperature scanning tunneling microscope
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中文总结 AI 辅助
本研究开发了一种集成于毫开尔文STM探头的微型蒸发器，可在接近5 K时原位向MgO/Ag(100)沉积孤立Fe原子，通量稳定且寿命长，无需额外部件即可保留同一表面区域的可及性。
中文摘要 AI 辅助
在低温扫描隧道显微镜（STM）中，将稀原子系综沉积到冷样品上颇具挑战性，因为辐射屏蔽和受限的内部几何结构常阻碍直接沉积路径，尤其在专为毫开尔文（millikelvin）操作设计的仪器中。我们展示了一种紧凑的毫瓦级蒸发源，其由商用微型白炽灯制成，直接集成到毫开尔文STM探头中。暴露的钨丝涂有微米级厚度的铁（Fe）薄膜，且位于距样品约1厘米处。我们在显微镜接近5 K运行时，将孤立Fe原子沉积到MgO/Ag(100)上。蒸发仅使STM主体温度升高约2 K，沉积后可轻易扫描同一纳米级表面区域，横向位移小于5 nm。显示对称非弹性台阶（位于±14 mV附近）的微分电导谱，将MgO上的沉积原子识别为Fe。从STM图像估算，局部沉积通量为1.5×10⁻⁵ nm⁻²·s⁻¹，对应标称蒸发器寿命约150小时。该固定蒸发器可实现重复低通量沉积，无需室温视线、可移动辐射屏蔽，或冷却后机械操作蒸发器，同时保留沉积前后同一原子级表面区域的可及性。
英文摘要
Depositing dilute atomic ensembles onto cold samples is challenging in low-temperature scanning tunneling microscopes (STM) because radiation shields and restricted internal geometries often preclude a direct deposition path, particularly in instruments designed for millikelvin operation. We present a compact, milliwatt-range evaporation source fabricated from a commercial miniature incandescent lamp and integrated directly into a millikelvin STM head. The exposed tungsten filament is coated with a micrometre-thick Fe film and positioned about 1 cm from the sample. We deposit isolated Fe atoms onto MgO/Ag(100) while operating the microscope near 5 K. Evaporation increases the STM-body temperature by only about 2 K, and the same nanoscopic surface region can be readily scanned after deposition with a lateral displacement of less than 5 nm. Differential-conductance spectra displaying symmetric inelastic steps near $\pm$14 mV identify the deposited atoms on MgO as Fe. From STM images, we estimate a local deposition flux of $1.5\times10^{-5}~\mathrm{nm^{-2}\,s^{-1}}$, corresponding to a nominal evaporator lifetime of ~150 h. The fixed evaporator enables repeated low-flux deposition without a room-temperature line of sight, the need for movable radiation shields, or mechanical evaporator access after cooldown, while preserving access to the same atomic-scale surface region before and after deposition.
