Fig. 1. Schematic diagram of high-resolution direct laser writing lithography based on phase change thin film

Fig. 2. Multiscale lithography characteristics of AIST thin film^[23]. Temperature field and phase transition region distributions at (a)(b) 200 ns, (c)(d) 600 ns, and (e)(f) 1 μs; (g) scanning electron microscope (SEM) image of multiscale dot array; (h) optical image of exposed pin structure and selected electron diffraction results, illustrated as schematic diagram of exposure needle structure; (i) SEM image of photon sieve, illustrated as magnified image of corresponding area; (j) SEM image of resolution test plate; (k) SEM image of arbitrary structure

Fig. 3. Electrochemical development strategy and high-resolution nanostructure of AIST thin film^[24]. (a) Temperature and surface potential distributions of arbitrary pattern exposure; (b) electrochemical development process; (c)‒(h) SEM images of multifunctional metasurface micro-nano structures

Fig. 4. SEM images of AIST thin film pattern transferred to Cr thin film and silica glass^[25-26]. (a) Five-pointed stars on Cr thin film, illustrated as magnified image; (b) nano cross structures on Cr thin film; (c) Fresnel zone plate on silica glass, illustrated as magnified image of selected area; (d) rectangular grid on silica glass, illustrated as magnified image of selected area; (e) nanocolumns on silica glass; (f) cross-grid structures on silica glass

Fig. 5. Positive/negative photolithographic conversion characteristic of NSb₂Te film with different atomic number fractions^[27]. (a) 0;

Fig. 6. Electrochemical development characteristic and development selectivity of NSb₂Te thin film. (a)‒(c) Potentiodynamic polarization curves^[27], (d)(e) electrochemical impedance spectra, and (f) equivalent circuit model of NSb₂Te thin films with different N atomic number fractions in TMAH solution^[27]; etch rates and development selectivities of NSb₂Te thin films in (g) H₃PO₄ solution and (h) HNO₃ solution^[28]; (i) SEM image of nanostructures^[28]

Fig. 7. High-resolution dry-lithography characteristic of AgSb₄Te thin film^[29]. Influence of (a) developing power, (b) air pressure, and (c) CHF₃ flow on development rate and selection ratio of as-deposited and exposed thin film; (d) AFM image of nanogratings; (e) SEM image of nanohole array; (f) AFM image of font structure

Fig. 8. Positive/negative lithography characteristics and mechanism of Ge₂Sb_1.8Bi_0.2Te₅ thin film. Relationship between etching depth of thin film and time in (a) KOH/H₂O₂ and (b) HNO₃/H₂O₂ solutions^[35]; (c)(d) AFM images of development morphology^[35]; (e) Lewis structure of amorphous Ge₂Sb_1.8Bi_0.2Te₅ thin film with polar covalent bond and lone-pair electron^[36]; (f) resonant structure of crystalline Ge₂Sb_1.8Bi_0.2Te₅ thin film with resonant bond^[36]; (g) AFM image of grating structure of Ge₂Sb_1.8Bi_0.2Te₅ thin film developed by TMAH solution^[38]; (h) relationship between etched height and time in amorphous region and crystalline phase exposure region of Ge_1.5Sn_0.5Sb₂Te₅ thin film^[39]

Fig. 9. Etching selectivity and mechanism of Si substrate to Ge₂Sb_1.8Bi_0.2Te₅ thin film. Influence of (a) SF₆ flow, (b) etching power, and (c) pressure on etching rate and etching selectivity of Ge₂Sb_1.8Bi_0.2Te₅ thin film and Si^[40]; (d) enhancement effect of Ge₂Sb_1.8Bi_0.2Te₅ thin film with increasing atomic number fraction of Bi^[36]

Fig. 10. Dry development characteristic and mechanism of Ag doped Ge₂Sb₂Te₅ thin film^[41]. (a) SEM image of developed grating structure, illustrated by AFM image of exposed sample (left) and magnified image of developed grating structure (right)^[41]; (b) corresponding cross-sectional diagram^[41]; (c) transmission electron microscopy (TEM) cross sectional image^[41]; (d) XRD pattern^[41], (e) Raman spectra, and (f) X-ray photoelectron spectroscopy (XPS) results before and after exposure^[41]

Fig. 11. Morphology and mechanism of TeO_x thin film in high resolution direct laser writing lithography. (a) Sample structure^[42]; (b) TEM cross-section image^[42]; SEM images of high-resolution nanostructures with feature sizes of (c) 110 nm, (d) 90 nm, (e) 80 nm, and (f) 11 nm^[42]

Fig. 12. Characteristic and mechanism of ZnS/SiO₂ thin film in high resolution direct laser writing lithography^[45]. (a) ZnS/SiO₂ nanopillar array structure; (b) curve of nanopillar diameter with laser pulse width; (c) nanopillar structure of quartz substrate; (d) model of development selectivity mechanism

Fig. 13. Nanolithography and local thermal induced nanolithography characteristic of Ti thin film based on two laser beams overlapping method. (a) Lithography schematic diagram of Ti thin film^[49]; (b) optical image of nanogap electrode arrays, illustrated by high-resolution SEM image of single nanogap electrode^[49]; (c) relationship between absorption coefficient and annealing temperature of S1805 photoresist at 532 nm^[50]; (d) distribution of light intensity in focusing region and temperature distribution on photoresist surface^[50]; (e) SEM images of grating nanostructures fabricated at laser powers of 2, 2.5, 3, and 4 mW (from top to bottom)^[50]

Fig. 14. Characteristic and mechanism of high resolution direct laser writing lithography of organic phase change thin film^[56]. (a) Lithography process; (b) schematic diagram of structure of nanopore, illustration is thermogravimetric and differential thermal analysis (top) and SEM image of nanopore (bottom); (c) molecular structure of organic phase change thin film; (d) SEM image of hole array with feature size of 40 nm; (e) silicon moth eye structure with half distance of 90 nm and depth of 100 nm; (f) silica thin net structure with half distance of 170 nm and depth of 50 nm; (g) deep groove structure with half distance of 200 nm and depth of 900 nm; (h) SEM image of sapphire hole structure with half distance of 200 nm and depth of 90 nm

Fig. 15. Applications of diffractive optical elements. (a) Morphology of diffraction optical element of silica glass^[24]; (b) SEM image of cross-section of grating structure^[24]; (c) 1st order beam intensity map of grating measured by X-ray with photon energy of 10 keV^[24]; (d) detector spatial data revealing grating diffraction at distance of 21 m downstream of grating^[24]; (e) intensity distribution from detector across grating diffraction stage to the 6th stage^[24]; (f) experimental and theoretical diffraction efficiency of various diffraction orders (-4th to +4th)^[24]; (g) SEM image of line grating cross-sectional etched on diamond substrate^[25]; (h) relationship between photon energy and theoretical diffraction efficiency^[25]; (i) optical image of grating structure with size of 2.5 inch of silica glass^[26]; (j) SEM image of grating structure illustrated with magnified grating structure^[26]; (k) theoretical and experimental diffraction efficiency of grating structure^[26]

Fig. 16. Applications of phase change memory, nanosensing chip, and tunable perfect absorber. (a) Optical morphology of cylindrical CSb₂Te₃ phase change memory device element arrays^[67]; (b) device unit performance after SET/RESET operation^[67]; (c) cycle stability of device unit after SET/RESET operation^[67]; (d) optical image of nanosensor component array^[49]; (e) Raman spectra of R6G measured along line of 5 nm nanogap electrode arrays^[49]; (f) Raman spectra of R6G at different nanogap electrodes^[49]; (g) Raman spectra of R6G at 5 nm nanogap electrodes with different bias voltages^[49]; (h) schematic diagram of tunable perfect absorber based on AgSb₄Te phase change thin film^[29]; (i) tunable absorption performance of tunable perfect absorber based on AgSb₄Te Phase change thin film^[29]

Fig. 17. Applications of grayscale/color image printing. (a)‒(c) Complex grayscale images printed onto Ge₂Sb₂Te₅ thin film^[68]; (d) color generation schematic of “(ZnS/SiO₂)/Ge₂Sb₂Te₅/glass substrate” stacked thin films^[69]; (e) laser direct writing color print image^[69]