{'fraction_non_alphanumeric': 0.02569750367107195, 'fraction_numerical': 0.008076358296622614, 'mean_word_length': 5.13963963963964, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Vacancy-assisted selective detection of low-ppb formaldehyde in two-dimensional layered SnS2.

Two-dimensional layered SnS2 film synthesized by thermal-CVD method is utilized for detecting formaldehyde (HCHO), which causes sick building syndrome. Back-gated field-effect transistor (FET) based SnS2 sensor successfully detects HCHO with concentrations down to 1 ppb in nitrogen atmosphere. Sensing measurements performed under dry air condition also exhibit a clear response to 20 ppb of HCHO, which is more sensitive than previously reported sensors based on other 2D-layered materials. Moreover, it is found that the sensor possesses a high selectivity for HCHO over other organic species. Theoretical calculations suggest that native sulfur vacancies existing in n-type SnS2 crystal play an important role in HCHO detection. Actually, oxygen atoms that are unexpectedly detached from HCHO molecules are found to fill the vacancies, giving rise to p-type doping in SnS2. As a result, decrease in the drain current of SnS2-FET can be found as a signal of HCHO detection. Furthermore, considering future mass-production of sensors, we demonstrate large-scale growth of SnS2 film by means of magnetron sputtering deposition and subsequent annealing in a diluted hydrogen sulfide atmosphere. The sputtered film is also found to show a good sensing ability to HCHO.