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EDXR-AFM

ED X -ray reflectometer with integrated AFM 

Barbara Paci  -

Laboratory: X-ray spectroscopy laboratory

Rome - Tor Vergata
 
Energy Dispersive X-Ray Reflectometry (EDXR) is based on the advantages of the ED technique over the angular dispersive traditional counterpart, utilizing a continuum spectrum radiation (the Bremsstrahlung of an X-ray tube- no monochromator required), while maintaining the scattering angle fixed. For in situ time resolved experiments, the advantages of the EDXR mode are considerable: the fixed experimental geometry during the acquisition - fundamental for in situ studies; the gain of about an order of magnitude in the energy of the incident beam and in the signal intensity, thanks to the use of the white beam and the simultaneous acquisition of data (by means of a solid state detector (SSD) sensitive to the energy of the X-rays). In the extremely grazing geometry required to perform XRR measurements, any misalignments during angular scanning can induce significant experimental errors, which are avoided in ED mode. On the other hand, this type of signal is not affected by the decrease in resolution due to the use of the SSD. To perform time resolved measurements of evolving systems, parallel data collection in the whole selected reciprocal space and the enhanced signal intensity are essential in order to collect “photos” of the systems under investigation representative of a relevant time scale and thus allow to follow the chemical/physical phenomena evolution. The possibility of using an AFM that plays the role of the sample holder also allows to obtain separated information in the reciprocal and direct space, with particular interest for phenomena related to surfaces and interfaces.
 
 

TECHNICAL SPECIFICATIONS

  • Siefert 3.5KW Generator: typical working conditions  E=55 kV, I=40 mA max.
  • X-Ray sources with W and Ag anode
  • ORTEC Ge-Single crystal solid state detector
  • ORTEC-ADCAM Electronic data acquisition 
  • In House acquisition software
  • Motorized arms, max 32°for each arm
  • W collimation slits (square or rectangular collimation) : max collimation 20*20 μm
  • Step-motor cradle
  • Continuous double axis cradle
  • Manual and motorized translators (x-y)
  • Standard sample holder, especially designed sample holders for controlled atmosphere and thermal treatments up to 200°C max.
  • Integrated AFM sample holder

AVAILABLE TECHNIQUES

  • Classical EDXR
  • In-situ EDXR
  • Time-resolved EDXR
  • Joint EDXR/AFM
 

SAMPLE

  • FThin films: film thickness 40-3000Å; max sample thickness 3cm; max in plane dimensions 10cm*10cm..

  • Multilayered samples: max. thickness for each layer 40-3000Å; total sample thickness max 3cm; in plane max. dimensions 10cm*10cm.

  • Samples to be measured in controlled atmosphere or in temperature, max in plane dimensions 2cm*2cm.

 

USE FOR

  • Determining morphological parameters as thickness and roughness of thin films/multilayers.
  • Determining electron density of thin films/multilayers.
  • In situ time resolved monitoring of morphological parameters evolution for thin films/multilayers as a function of external conditions: ambient conditions, controlled atmospheres, polluting gasses, thermal treatments, light exposure.  
  • In situ time resolved electron density monitoring of thin films/multilayers as a function of external conditions: ambient conditions, controlled atmospheres, polluting gasses, thermal treatments, light exposure.
 
 

Case Studies

Extending the Continuous Operating Lifetime of Perovskite Solar Cells with a Molybdenum Disulfide Hole Extraction Interlayer.
 
Lead halide perovskite solar cells are one of the most promising photovoltaic technologies. Here, it is shown how the introduction of MoS2 flakes as a hole transport interlayer significantly improved the stability of encapsulated devices Such effects ascribed to the twofold beneficial role of MoS2,inhibiting both interface and structural aging pathways, as demonstrated by XRD and EDXR experiments.
 
See: G.Kakavelakis, I.Paradisanos, B.Paci, et al. Adv. Energy Mater. 2018, 1702287
 
See news:
http://grafene.cnr.it/celle-solari-a-perovskite-piu-stabili-grazie-a-cristalli-bidimensionali/  
 
https://www.cnr.it/it/news
 
See twitter:
https://twitter.com/graphenefactory/status/1005019272559693826

 
 
 
 

Conductivity via Thermally Induced Gap States in a Polyoxometalate Thin Layer.  
 
Polyoxometalates are as an emerging class of materials in organic optoelectronics. X-ray reflectivity is used for determination of layer thicknesses and scattering length densities: nanostriped films a few tens of nm thick can be obtained and that such structuring is accompanied by the appearance of gap states and by a switch from an insulating to a conductive state. Integrating the layer into an organic photovoltaic device the conduction through it thanks to favorable band alignment between ITO, the gap states, and the active photovoltaic layers.  
 
See: Qirong Zhu, Barbara Paci et al. J. Phys. Chem. C 2019, 123, 1922−1930

 
 
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