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掃描開爾文探針顯微術在超薄膜表徵應用

Scanning Kelvin Probe Microscopy for Ultra-thin Film Characterization

摘要


原子力顯微鏡(atomic force microscopy, AFM)是一種掃描探針技術,可以非常高分辨率地成像表面形貌。AFM還可以通過探針與樣品表面間作用力,進而獲得表面物理化學資訊,例如表面形貌、顆粒尺寸分析、表面粗糙度、電性、壓電性、鐵電性或磁性等。奈米表面科學的研究如雨後春筍般蓬勃發展。如今AFM也衍生出許多模組化功能。在這項研究中,我們將探討掃描開爾文探針顯微鏡(scanning Kelvin probe microscopy, SKPM)的應用。SKPM是一種基於AFM的技術,通過檢測導電探針和樣品表面之間的電容力來測量表面電位。這些力可以通過在針尖(或樣品)上施加適當的偏壓來補償,其值取決於由於針尖和樣品功函數之間的差異而產生的電容大小。因此,所施加的偏置值等於(和相反)尖端與樣品之間的表面電位差。AFM在掃描形貌時測量這些值的過程,可以生成與結構相關的表面電位圖像或形貌圖。此外,我們可以通過將表面電位轉換為功函數來表徵表面電性能的變化。我們還使用SKPM研究濕度對鈣鈦礦薄膜表面電勢/功函數的影響。SKPM的應用將改善我們對這些鈣鈦礦表面電異質性的理解,使我們能夠定位和識別缺陷部位,並為改進工藝提供有價值的意見。我們為表徵和優化這些材料的性能而做出的努力將導致鈣鈦礦基材料和設備的穩定性,更高的性能以及更長的使用壽命。此技術有助於未來瞭解導電/半導體材料(如:晶圓或電晶體)表面電性異質區或定位缺陷位置,進而找出缺陷的源頭並加以改善。對於未來在光電元件穩定性的改善非常重要。

並列摘要


Atomic force microscopy (AFM) is a scanned probe technique that images surface topography with very high resolution. The AFM can also measure and map a wide range of additional physical (and chemical) properties through the interaction between the AFM probe and a sample surface. Surface roughness, electric and magnetic field gradients, surface potential, conductivity, capacitance, ferroelectric and piezoelectric phenomena, thermal conductivity, and nanomechanical properties, can all be measured simply by using an appropriate probe and instrument setup. Once collected, these data may be mapped onto topography for direct correlation with surface structure. Due to its versatility for nanoscale property mapping, the AFM has had a significant effect on the emergent fields of Nanotechnology and Advanced Materials research. In this study, we will explore applications of scanning Kelvin probe microscopy (SKPM). SKPM is an AFM based technique that measures the surface potential by detecting capacitive forces between a conductive probe and a sample surface. These forces can be compensated by applying an appropriate bias to the tip (or sample), the value of which depends on the magnitude of the capacitance which arises due to differences between the tip and sample work functions. The applied bias value is thus equal (and opposite) to the surface potential difference between the tip and sample. The AFM measures these values while scanning topography and can then generate a surface potential image or map correlated to structure. Further, we can characterize changes in surface electrical properties by converting surface potential into work function. We will use SKPM to investigate the influence of humidity on the surface potential/work function of perovskite films. Application of SKPM will improve our understanding of electrical heterogeneity at these perovskite surfaces, allow us to locate and identify defect sites, and provide valuable input for process improvement. Our efforts to characterize and optimize the behavior of these materials will lead to improved stability, higher performance, and longer lifetimes of perovskite based materials and devices.

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