Investigation of shadow effect in laser-focused atomic deposition

Fabrication and measurement of traceable pitch standard with a big area at trans-scale

“…The feature width broadening and height increasing of the Cr nanostructure have been experimentally observed in the gradual atom flux distribution divergent area on one sample along the standing wave direction. [19] Meanwhile, the Gaussian distribution of the laser standing wave makes its corresponding PTVH conform with a Gaussian distribution. In the experiment, the relative position of the standing wave and the substrate is a key issue for atom deposition.…”

Study of interferometric signal correction methods in ultra-precision displacement measurement

“…However, as the demand for higher resolution in precision measurement increases, so does the inscribed density of the reference grating for grating interferometers, e.g. the ultra-high inscribed density self-traceable grating at Tongji University has a period of 212.8 nm, producing a signal period of 106.4 nm at half wavelength, which is less than the minimum signal period value of 128 nm produced by Heidenhain's displacement measurement technique using a glass-ceramic substrate grating as a scale [3,4,21]. The high density of grating inscriptions and the finer the grating pitch, combined with the process limitations of the instrument itself, result in three main sources of error in the ultra-precision grating interferometric signal in displacement measurement: (1) at the same noise level, the single-period measurement step of the ultraprecision grating interferometric signal is relatively small, and the impact of the error on the signal becomes larger; (2) at the same acquisition frequency and within the same measurement time, the ultra-precision grating interferometric signal acquires more outliers.…”

“…The ultra-precision measurement of displacement is the foundation for the rapid development of modern ultra-precision machining, integrated circuits, precision scientific instruments and other fields. The ultra-high line density grating and grating interferometer are key components for precise displacement measurement and control [1][2][3][4][5]. Increasing the grating line density can effectively reduce the raw signal of displacement measurement and improve the displacement measurement resolution [2].…”

“…The high density of grating inscriptions and the finer the grating pitch, combined with the process limitations of the instrument itself, result in three main sources of error in the ultra-precision grating interferometric signal in displacement measurement: (1) at the same noise level, the single-period measurement step of the ultraprecision grating interferometric signal is relatively small, and the impact of the error on the signal becomes larger; (2) at the same acquisition frequency and within the same measurement time, the ultra-precision grating interferometric signal acquires more outliers. (3) Fluctuations in the wavelength of the laser source, environmental changes, inaccurate optical circuit mounting, unsatisfactory performance of the optics, and processing of the raw signal by the photodetector and subsequent processing circuitry can all bias the measurement results. For problem (3), Heydemann proposed a phase error correction model for orthogonal interferometric signals in 1981 and used a least squares non-linear fit to eliminate the nonlinear error [22]; Wu and Eom of Physikalisch-Technische Bundesanstalt (PTB) carried out a detailed analysis of the nonlinear error, confirming that it is caused by the performance of the light source and optical components as well as interferometer adjustment errors, and claiming that its response to signal as the phase calculation error of the interferometric signal with unequal amplitude, non-orthogonal phase, and DC offset [23]; further, Jin et al studied the improvement based on the above conclusion [24][25][26][27][28].…”

Natural square ruler at nanoscale

“…The detailed experimental setup in our laboratory was described in previous studies. [28][29][30][31] Figure 4 shows AFM images of the two-step laser-focused atomic depositions with rotation angles of 45°and 90°. As expected, a highly uniform rhombus array of dots was fabricated at the interlaced positions in both situations; the distance between each pair of parallel sides in the rhombus shape is expected to be 212.8 nm, determined by the half-wavelength of the laser.…”