Atom probe tomography analysis of poly(3‐alkylthiophene)s

Abstract

SummaryPulsed-laser atom-probe tomography is used to compare the field-evaporation mass spectrum and spatial distribution of molecular fragments from various poly(3-alkylthiophene) films deposited on sharpened aluminium specimen carriers using two different deposition methods. Films deposited via a modified solution-cast methodology yield small fragments with a uniform structural morphology whereas films deposited via an electrospray ionization methodology yield a wide range of fragments with a very non-uniform structural morphology. The main field-evaporated chemical species identified for both deposition types were, in order of typical relative abundance, C 2 H 5 + , CH 3 + , C 2 H 4 + , followed by C 3 H 7,8 + /SC + and SCH + . Thick electrospray depositions allowed investigation of the influence of laser-pulse energy on the analysis. Evidence is presented supporting the presence of a critical laser-pulse energy whereby changes in film morphology are signalled by the appearance of a new mass fragment at 190 Da.

Chemical mapping of mammalian cells by atom probe tomography

“…The technique is based on a phenomenon called field evaporation, where ions are desorbed from a needle-shaped sample by application of a very intense electric field (~ several volts per nanometer) under very high vacuum and at cryogenic temperatures, and then detected by a single-ion sensitive detector (Muller, 1956). Although the first atoms were successfully imaged in a field ion microscope more than half a century ago (Müller, 1951), recent significant advances in the technology now enable the routine spatial and compositional imaging of semiconductors (Gorman et al, 2007; Perea et al, 2006; Prosa et al, 2010b), alloys (Miller et al, 2005; Mousa et al, 2010) and polymers (Prosa et al, 2010a) for visualization of features such as grain boundaries (Colijn et al, 2004), coarse precipitates (Kvist et al, 1996) and subsurface dislocations (Thompson et al, 2005). Three-dimensional compositional mapping is achieved by the use of a standing electric field in conjunction with either a pulsed electric fields or pulsed laser at the sample tip and coupled with a position-sensitive detector, allowing for time-of-flight mass spectrometric identification of each ion desorbed from a heterogeneous sample.…”

Organic Materials and Organic/Inorganic Heterostructures in Atom Probe Tomography

“…Compared to inorganic materials and organic thin films, atom probe spectra of soft polymeric materials can be much richer in terms of the number of fragments observed. For example, when P3HT was deposited on pre-sharpened tips by dipping or electrospray, many different molecular ions differing by as little as Dm/z = 1 were detected ( Figure 3A) [14]. Many of these correspond to a series of molecular ions with the general formula [C n H 2n±m ] + , where n = 1-6 and m is variable.…”

“…Laser pulsing heats the specimen tip surface, lowering the required electric field for field evaporation and, consequently, reducing premature specimen failure from stresses generated by the electric field. We discuss here the rapidly improving analysis capabilities for self-assembled monolayers [11][12][13], polymers [14][15][16], and the complex architecture of a tooth biomineral nanocomposite [17].…”

Focused ion beam fabrication of solidified ferritin into nanoscale volumes for compositional analysis using atom probe tomography

“…Ions originating from the apex are detected by a position‐sensitive detector combined with synchronized time‐of‐flight (TOF) measurements to reveal the chemical composition of small volumes of materials. APT has permitted the compositional mapping of nanoscale volumes of a range of complex crystalline and amorphous specimen types, such as organic materials (Prosa et al , 2009; Gault et al , 2010; Zhang & Hillier, 2010), biomaterials (Gordon & Joester, 2011), and oxide materials (Larson et al , 2008; Chen et al , 2009; Bachhav et al , 2011). Furthermore, complementary electron tomography and AP tomography may ultimately be possible with biological specimens similar to what has been reported for the same volume of an inorganic specimen (Arslan et al , 2008).…”