Rui Hu

A series of nonchemically amplified resists based on dibenzothiophenium-functionalized polystyrene (PSSDx, x is the loading ratio of the sulfonium, x = 0.5, 0.7, 1.0) were designed and prepared. The lithographic performance of PSSDx resists was evaluated by electron beam lithography (EBL). The PSSD0.7 resist exhibited superior resolution (20 nm) compared with PSSD0.5 (25 nm) and PSSD1.0 (22 nm) resists under the same EBL processing conditions. By reducing the film thickness to 25 nm, the PSSD0.7 resist resolved the 18, 16, and 15 nm L/S patterns at doses of 1200–1500 μC cm–2 with LERs of 3.0–3.3 nm, demonstrating a superior comprehensive performance to the previously reported triphenylsulfonium-based PSTS0.7 model resist (18 nm L/S at 2400 μC cm–2). The PSSD0.7 resist was further investigated by extreme ultraviolet lithography (EUVL), achieving an impressive 14 nm pattern with a line edge roughness (LER) of 3.0 nm at an exposure dose of 148 mJ cm–2. The quartz crystal microbalance (QCM) analyzer confirms that the solubility behavior of PSSD0.7 and PSTS0.7 model resist films is not the main reason for the difference in sensitivity. The calculation and photochemical kinetics study suggest that the significantly reduced bond energy and the enhanced efficiency and rate of the photochemical reaction with the dibenzothiophenium group play a key role in the excellent lithographic performances of the PSSD0.7 resist.

Transient spectroscopy of a B←O bond-cleavage-induced intramolecular charge-transfer molecule reveals the dissociation activation energy and the process of the concerted bond cleavage/charge transfer.

Elucidating the intricate mechanisms of excited state interactions within inorganic semiconductor-organic molecule conjugates is of great scientific and practical significance, as it enables the control of energy transfer and electron transfer processes across the inorganic-organic interface. Herein, we report the distinct excited state interactions upon selective excitation of individual components in a conjugate comprising perovskite nanocrystals (NCs) and the near-infrared (NIR) dye IR808. Transient absorption investigation reveals that upon excitation of IR808 by NIR light, electron transfer from excited singlet IR808 to the NCs occurs with a time constant of 8.2 ps. This is followed by charge recombination with a time constant of 407 ps, ultimately forming triplet IR808. In contrast, selective excitation of the NCs with red photons, a one-step triplet energy transfer (k_TET = 1.22 ns^-1) from the excited NCs to IR808 rather than stepwise charge transfers, is observed during the triplet IR808 formation. Energy transfer outcompetes charge transfers in this case despite both processes being thermodynamically favorable because charge transfer falls deeper into the inverted region of Marcus theory than the triplet energy transfer. Thermodynamics can govern the kinetics in the excited state interactions within NCs and organic hybrids, thereby enabling excitation wavelength-controlled excited state interaction pathways. The effective generation of triplet IR808 and the broad spectral response of the NCs-IR808 conjugate enable applications in the sensitization of singlet oxygen and photochemical upconversion through visible to NIR excitation.

Aryl sulfonate ester modified polystyrene with different substituents (X-SEPS, X = H-, MeO-, and CN-) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The excellent thermal stability and film-forming capability of these three polymers suggest that they can satisfy the lithography process and are candidates for resist materials. The comparative electron beam lithography (EBL) demonstrates that the three (H-SEPS, MeO-SEPS and CN-SEPS) resists exhibit different EBL performances. The calculation of the bond energies for model compounds suggests that the influence of substituent groups on the bond energy is not the main reason for their differences in sensitivity. A fully automated dissipative quartz crystal microbalance (QCM) analyzer confirms that the influence of the substituent groups on the solubility behavior of the resist films in developers leads to different photolithographic performances. H-SEPS resist exhibits a better comprehensive performance than that of MeO-SEPS and CN-SEPS resists, achieving an 18 nm line/space (L/S) pattern and a 10 nm line/4 space (L/4S) semi-dense pattern by EBL at doses of 3200 and 2800 μC cm^-2, respectively. Further extreme ultraviolet lithography (EUVL) demonstrates the capability of H-SEPS resist to form 22 nm half-pitch (HP) patterns. The detailed study of the photochemical reaction and patterning mechanism suggests that the decomposition of sulfonate ester groups into polar sulfonic acid groups, along with a rearrangement, leads to a solubility switch of resist films in the developer.

A non-chemically amplified molecular resist based on γ-hydroxy carboxylate and triphenylsulfonium groups was developed for EBL and EUVL, resolving 22 and 20 nm patterns at low exposure doses of 160 μC cm ⁻² and 13.3 mJ cm ⁻² , respectively.

Thermally activated sensitization of organic annihilators by a penta-nuclear Yb complex enables an anti-Stokes shift above 1.3 eV in photochemical upconversion.