Apertureless terahertz near-field microscopy

Abstract

Terahertz near-field microscopy may serve as a novel tool to measure the high-frequency permittivity of dielectric surfaces on submicrometre semiconductor structures. We present an apertureless THz near-field microscope, which allows for spatial resolutions as small as 150 nm. A new model has been developed that considers the field coupling the scanning probe with a sample and reproduces the image data qualitatively and quantitatively.

A study of background signals in terahertz apertureless near-field microscopy and their use for scattering-probe imaging

“…In the near-field regime, the antenna model described earlier [16,30] predicts that the near-field signal is approximately proportional to the time-integral of the incident electric field. This calculated time-integral signal is shown in Figure 3(a).…”

“…That said, it cannot be ignored as an experimental possibility, particularly when using a broadband THz source. The near-field signal is naturally low-bandwidth due to the approximate 1/w filtering due to antenna effects [16,30]. In contrast, the background signal is a timederivative, meaning its bandwidth can be considerably larger.…”

“…One consequence is that THz ANSOM analysis does not generally employ the polarizable-sphere model described above. Instead, an antenna model is used, in which the resulting ANSOM signal is proportional to the time-integral of the incident electric field [16,30] In THz applications, modulation of the tip-sample separation is also employed for background suppression, but since the THz-TDS system detects electric field rather than intensity, the analysis is significantly less complex than for intensity-detection schemes.…”

Full vectorial mapping of the complex electric near-fields of THz resonators

“…[3][4][5][6][7][8] Attempts to measure and characterize near-fields were done first at optical frequencies, which paved the way for near-field detection techniques at THz frequencies. [9][10][11][12][13][14][15][16][17][18][19][20] Owing to the relatively long wavelengths of THz radiation (∼100's of microns), the creation of highly confined THz local fields in small volumes is critical for enhancing the interaction of THz waves with matter. The use of resonant structures for this purpose has been the topic of many interesting studies, especially for spectroscopy of deep-subwavelength structures.…”

Uniquely Identifiable Tamper-Evident Device Using Coupling between Subwavelength Gratings

“…They have also been applied towards biosensing [8], guided optics [9], optical couplers [10], apertureless microscopy [11,12], nanoelectromechanical devices [13], and in nanoscale measurement [14]. [15] In [14], Rogers, et.…”