Hydrogen-rich solid thin layers - INTDS · Hydrogen-rich solid thin layers UNIVERSITY OF WARSAW Heavy Ion Laboratory 25thINTDS Conference, Vancouver, Canada 2010 A. Stolarz1, G. Sibbens2,

Hydrogen-rich solid thin layersHydrogen-rich solid thin layers

UNIVERSITY OF WARSAWUNIVERSITY OF WARSAW Heavy Ion LaboratoryHeavy Ion Laboratory

25th INTDS Conference, Vancouver, Canada 2010

A. Stolarz1, G. Sibbens2, A. Dean2, M. Józwik3, Y. Aregbe2

1 Heavy Ion Laboratory, University of Warsaw, Poland2 Institute for Reference Materials and Measurements, Geel, Belgium

3 Institute of Micromechanics and Photonics, Warsaw University of Technology, Warsaw, Poland



- as proton radiator at a recoil proton telescope (RPT) that are used for neutron flux measurements

- for determination of the cross section ratio of 235U(n,f) / H (n,n) reactions

octoconasol: C28H58O

polyethylene: C2H2

tristearin: C57H110O6

what for?



what was required?

thickness range 0.05 – 0.5 mg/cm2 (0.58 – 5.8 µm)

homomogeneity

stability over long period (special concern: humidity)

and

for RPT well defined geometry so it should be on a ridged backing

for cross-section ratio micro homogeneity

vacuum evaporation

melting point: 68 – 73 ºC (but could be as low as 55 ºC)



Tristearin deposit on 2 mm Si wafer, depo rate 5-6 Å/s.

80xTa boat with hollow ~2.5 cm



0.5-1.5 Å/s

rate

20-35 Å/s

35-100 Å/s



Si: 50 µg/cm2; 2.2 - 2.5 Å/s

quartz

Ta: 50 µg/cm2; 2.5 – 3 Å/sTa disc 0.1 mm thick

500 µg/cm2; 30-100 Å/s



Ta: 50 µg/cm2; 2.5 – 3 Å/s

Ta: 100 µg/cm2; 5.5 - 6 Å/s



trist - ~50 µg/cm2

polyimide foil - ~30 µg/cm2

rate: 1.3 -1.5 Å/s

(100x)

from AFM focusing microscope

500x

tris on PI



Trist ~40 µg/cm2

deposited on polyimide foil ~ 30 µg/cm2 backed by 2.5 mm Cu rate: 1.5-1.7 Å/s (100x)

tris on PI+Cu


25th INTDS Conference, Vancouver, Canada 2010 tris on PI+Cu



depo quality strongly depends on the heat trasfer

q = k A dt/s

k -thermal conductivity coeff.

dt -temp. grandient across the material

A -area

s -thickness

q ≈ k/s

s Si = 2 mm k = 150 W/(m×K)

s Ta = 0.1 mm k = 57 W/(m×K)



thickness determination:- by quartz balance: needed acoustic impedance

value for tristearin estimated as 1.15 x105 g cm-2 s-1, based on weighing the known area (approach via values found for fat and paraffin)

- mass/area: samples prepared on 5 µm aluminium foil and on Ta 0.1 mm thick discs

- AFM and optical profilometry



thickness and its homogeneity

?0.600.56 - 7Ta 3

?1.231.15.5Ta 2

?0.640.52.3 - 2.7Ta 1

9582

92.4 %77 %

1.040.86

0.69-0.720.53-0.62

-1.121.12

25 – 302 - 7

Si 161

89 -9083

91%73.2 %

0.500.40

0.32-0.370.25-0.3

-0.550.55

25 – 302.5 - 3.0

Si 49

83 %4.563.1-5.5 30 -110Si 4747103 %0.380.19-0.37 0.5-0.7Si 44

homogenity

%

% of quartz indic.

OP corrected ntris=1.47

OP [ µm ]

weighing[µm]

quartz [µm]

rate [Å/s]

sample



Soft, low melting point deposits as tristearin should be prepared onbackings assuring good heat transfer as grain size, layer homogeneity is dependent on heat dissipation from backing.

Taking into account demand of ‘rigid’ geometry for proton telescopes may be thin Si wafer (instead of Ta) should be taken into consideration as backing as Si has much better heat conductivity.

Hydrogen content in the samples as for the moment is defined by weighing and molecular stoichiometry.



Acknowledgement:

Work was partly supported by FP6 EFNUDAT project.

Documents

Hydrogen-rich solid thin layers - INTDS · Hydrogen-rich solid thin layers UNIVERSITY OF WARSAW Heavy Ion Laboratory 25thINTDS Conference, Vancouver, Canada 2010 A. Stolarz1, G. Sibbens2,