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Layer-Resolved Evolution of Organic Thin Films Monitored by Photoelectron Emission Microscopy and Optical Reflectance Spectroscopy.

Ghanbari E, Wagner T, Zeppenfeld P - J Phys Chem C Nanomater Interfaces (2015)

Bottom Line: In this paper, we present the first experiment in which both techniques have been applied simultaneously and synchronously.We illustrate how the combined PEEM and DRS results can be correlated to obtain an extended perspective on the electronic and optical properties of a molecular film dependent on the film thickness and morphology.As an example, we studied the deposition of the organic molecule α-sexithiophene on Ag(111) in the thickness range from submonolayers up to several monolayers.

View Article: PubMed Central - PubMed

Affiliation: Institute of Experimental Physics, Johannes Kepler University , Altenberger Str. 69, 4040 Linz, Austria.

ABSTRACT

Photoelectron emission microscopy (PEEM) and differential (optical) reflectance spectroscopy (DRS) have proven independently to be versatile analytical tools for monitoring the evolution of organic thin films during growth. In this paper, we present the first experiment in which both techniques have been applied simultaneously and synchronously. We illustrate how the combined PEEM and DRS results can be correlated to obtain an extended perspective on the electronic and optical properties of a molecular film dependent on the film thickness and morphology. As an example, we studied the deposition of the organic molecule α-sexithiophene on Ag(111) in the thickness range from submonolayers up to several monolayers.

No MeSH data available.


Selected PEEM images recorded during the depositionof α-6Ton a Ag(111) surface held at 331 K (Figure 2). The images were taken at times 1–4marked in Figure 2:(1) maximum intensity of the PEEM transient, corresponding to thecompletion of the first α-6T monolayer; (2) half way duringthe formation of the second monolayer; (3) onset of 3D growth aftercompletion of the second monolayer; and (4) thick film (nominal coverage∼8 ML) showing α-6T crystallites on top of the 2 ML thickwetting layer. The images of the lower row correspond to a field ofview of 145 μm. The images in the top row show an enlarged viewof the 40 × 40 μm2 area indicated in the imagesin the bottom row. The color coding of the frames matches the onein Figure 4. The fullimage sequence is available as Supporting Information.
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fig3: Selected PEEM images recorded during the depositionof α-6Ton a Ag(111) surface held at 331 K (Figure 2). The images were taken at times 1–4marked in Figure 2:(1) maximum intensity of the PEEM transient, corresponding to thecompletion of the first α-6T monolayer; (2) half way duringthe formation of the second monolayer; (3) onset of 3D growth aftercompletion of the second monolayer; and (4) thick film (nominal coverage∼8 ML) showing α-6T crystallites on top of the 2 ML thickwetting layer. The images of the lower row correspond to a field ofview of 145 μm. The images in the top row show an enlarged viewof the 40 × 40 μm2 area indicated in the imagesin the bottom row. The color coding of the frames matches the onein Figure 4. The fullimage sequence is available as Supporting Information.

Mentions: Figure 2 shows a PEEM transient of the local electronyield(LEY) for p-polarized light (Figure 2a) together with the DRS signal ΔR/R0 at a photon energy of 2.3 eV (Figure 2b) recorded simultaneouslyduring the deposition of α-6T on a clean Ag(111) surface heldat 331 K. The PEEM transient shown in Figure 2a was obtained by processing each of morethan 1000 PEEM images recorded each 1.2 s during the growth experiment.Selected PEEM images are depicted in Figure 3. The solid cyan line in Figure 2a represents the mean valueof the electron yield, averaged over the entire field of view (∼145μm) of each image. A gray scale representation of the histograms,which were calculated for the intensity distribution of each PEEMimage, is found underneath the cyan line. Darker shades of gray indicatea higher probability of finding a particular LEY value at time t. Therefore, the blackness and width of the gray band underneaththe cyan line is a measure of the spatial variation of the photoemissionyield at a given time t.


Layer-Resolved Evolution of Organic Thin Films Monitored by Photoelectron Emission Microscopy and Optical Reflectance Spectroscopy.

Ghanbari E, Wagner T, Zeppenfeld P - J Phys Chem C Nanomater Interfaces (2015)

Selected PEEM images recorded during the depositionof α-6Ton a Ag(111) surface held at 331 K (Figure 2). The images were taken at times 1–4marked in Figure 2:(1) maximum intensity of the PEEM transient, corresponding to thecompletion of the first α-6T monolayer; (2) half way duringthe formation of the second monolayer; (3) onset of 3D growth aftercompletion of the second monolayer; and (4) thick film (nominal coverage∼8 ML) showing α-6T crystallites on top of the 2 ML thickwetting layer. The images of the lower row correspond to a field ofview of 145 μm. The images in the top row show an enlarged viewof the 40 × 40 μm2 area indicated in the imagesin the bottom row. The color coding of the frames matches the onein Figure 4. The fullimage sequence is available as Supporting Information.
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Related In: Results  -  Collection

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fig3: Selected PEEM images recorded during the depositionof α-6Ton a Ag(111) surface held at 331 K (Figure 2). The images were taken at times 1–4marked in Figure 2:(1) maximum intensity of the PEEM transient, corresponding to thecompletion of the first α-6T monolayer; (2) half way duringthe formation of the second monolayer; (3) onset of 3D growth aftercompletion of the second monolayer; and (4) thick film (nominal coverage∼8 ML) showing α-6T crystallites on top of the 2 ML thickwetting layer. The images of the lower row correspond to a field ofview of 145 μm. The images in the top row show an enlarged viewof the 40 × 40 μm2 area indicated in the imagesin the bottom row. The color coding of the frames matches the onein Figure 4. The fullimage sequence is available as Supporting Information.
Mentions: Figure 2 shows a PEEM transient of the local electronyield(LEY) for p-polarized light (Figure 2a) together with the DRS signal ΔR/R0 at a photon energy of 2.3 eV (Figure 2b) recorded simultaneouslyduring the deposition of α-6T on a clean Ag(111) surface heldat 331 K. The PEEM transient shown in Figure 2a was obtained by processing each of morethan 1000 PEEM images recorded each 1.2 s during the growth experiment.Selected PEEM images are depicted in Figure 3. The solid cyan line in Figure 2a represents the mean valueof the electron yield, averaged over the entire field of view (∼145μm) of each image. A gray scale representation of the histograms,which were calculated for the intensity distribution of each PEEMimage, is found underneath the cyan line. Darker shades of gray indicatea higher probability of finding a particular LEY value at time t. Therefore, the blackness and width of the gray band underneaththe cyan line is a measure of the spatial variation of the photoemissionyield at a given time t.

Bottom Line: In this paper, we present the first experiment in which both techniques have been applied simultaneously and synchronously.We illustrate how the combined PEEM and DRS results can be correlated to obtain an extended perspective on the electronic and optical properties of a molecular film dependent on the film thickness and morphology.As an example, we studied the deposition of the organic molecule α-sexithiophene on Ag(111) in the thickness range from submonolayers up to several monolayers.

View Article: PubMed Central - PubMed

Affiliation: Institute of Experimental Physics, Johannes Kepler University , Altenberger Str. 69, 4040 Linz, Austria.

ABSTRACT

Photoelectron emission microscopy (PEEM) and differential (optical) reflectance spectroscopy (DRS) have proven independently to be versatile analytical tools for monitoring the evolution of organic thin films during growth. In this paper, we present the first experiment in which both techniques have been applied simultaneously and synchronously. We illustrate how the combined PEEM and DRS results can be correlated to obtain an extended perspective on the electronic and optical properties of a molecular film dependent on the film thickness and morphology. As an example, we studied the deposition of the organic molecule α-sexithiophene on Ag(111) in the thickness range from submonolayers up to several monolayers.

No MeSH data available.