Fig. 1: Atomic-scale scanning tunneling microscopy (STM) characterization of the C-chain analogs.
From: n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics
a Large-scale STM micrograph of C-analogs condensed on Au(111) surface. The substrate is chosen to permit efficient tunneling conditions while preserving the intrinsic C-analog properties due to the low reactivity of gold surfaces toward molecular adsorbates. The STM parameters are 14 × 14 nm2, V = 1.4 V, I = 10 pA. b Detail of the 2D crystallites found within the C-analog condensed region, 7 × 7 nm2, V = 1.4 V, 20 pA. c High-resolution image of the linear structures. A wiggling intramolecular resolution is observed in the tunnel channel. 2 × 2 nm2, V = 1.5 V, I = 0.5 nA. d Histogram of the length distribution of the C-chains. The events have been binned by 1.2 Å, which corresponds to the CH2–CH2 distance in the aliphatic chains. Therefore, the number of events per channel corresponds to the number of molecules measured for a particular carbon length. The number of chains inspected is 232. The yellow-marked part of the histogram represents the range in which alkanes with small sizes do not efficiently adsorb on Au(111) due to a low sticking coefficient. e Profile obtained from the image shown in panel d, following the black dashed line. The periodicity of the wiggling pattern within the chains is 2.5 Å.
