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Tw o hom oleptic dithiocarbam ate precursors w ere investigated. These were [Sn(S2C N R2)4] w here R=M e, Et. Both w ere solids at room tem perature. Differential

scanning calorim etry was carried out to determ ine suitability of these as CVD precursors, and it was found that the boiling points w ere prohibitively high. W ith this in mind, the precursor was adm itted using the aerosol delivery m ethod. A small num ber of reactions w ere carried out using [Sn(S2C N M e2)4] and the bubbler delivery method,

5.4.1 Reactions carried out

R e a c tio n s in v o lv in g [S n (S2C N E t2)4] w ere c a rrie d o u t at th re e te m p e ra tu re s - 350, 4 50

an d 5 20 °C . [S n (S2C N E t2)4], 0.3 g, w as d isso lv e d in c h lo ro fo rm , 50 cm^, an d ad m itte d

u sin g the h u m id ifie r. N o h y d ro g e n su lfid e w as u se d in any re a c tio n , an d re a c tio n s w ere c a rrie d o u t until th e en tire p re c u rso r had run o u t (ty p ic a lly 30 m in). T in o x id e / silica co a te d g lass w as u sed as the su b strate.

F o r m e th o d o lo g y o f re actio n , re fe r to S ectio n 2.1, p a rtic u la rly 2.1.3 fo r aerosol m o d ific a tio n s.

5.4.2 Visual appearance of films

T h e film s d e p o site d fro m [S n (S2C N E t2)4] u sin g th e aero so l d e liv e ry m e th o d at 4 5 0 and

520 °C c o a te d o n ly the first c a . 10 cm o f the su b stra te . F ilm s w ere th in and grey in

co lo u r. N o film w as d e p o site d at 350 °C.

5.4.3 Raman microscopy

c

0 50 100 150 200 250 300 350 400

Wavenumber / cm-1

T h e R a m a n sp e c tra o f film s d e p o site d fro m [S n (S2C N E t2)4] w ere re co rd e d . T h e

sp ec tru m o f the film d e p o site d at 520 °C is sh o w n in F ig u re 5.15.

F ig u re 5.15 sh o w s the ch a ra c te ristic R am an sp e c tru m o f tin (II) su lfid e. T h e sp ectru m re c o rd e d fro m the film d e p o site d at 4 5 0 °C sh o w s the sam e p attern .

5.4.4 Energy dispersive analysis by X-rays

F D A X m e a su re d the elem e n ta l ra tio fo r both th e film s d e p o site d . A s the film s w ere d e p o site d on tin o x id e / silica co a te d g lass, e le m e n ta l ra tio s w ere fo u n d to be tin rich. S u lfu r w as o b se rv e d in the film s, alth o u g h at low lev els. A c c u ra te tin to su lfu r ratio s c o u ld n o t be d eterm in e d .

5.4.5 Scanning electron microscopy

S F M sh o w e d th at the film s w ere n o t u n ifo rm . Im ag e s o f each o f the film s d ep o sited

from [S n (S2C N F t2)4] are g iven in F ig u re 5.16. T h e se sh o w th a t th e film is d ep o site d in

large clu ste rs o f p artic le s. U n d e rn eath the p a rtic le s no m o rp h o lo g y is o b serv ed , so it w as th o u g h t th at th is is u n c o a te d glass.

A

150014 20KV X3!èèK'iè!èuK 2 5 0 0 1 1 25KV X3.50K 8 . 6 u a

5.4.6 Conclusions

In this section, only a small num ber of films w ere attem pted. O nly those reactions using the aerosol delivery m ethod could deposit a film. This was due to involatility of the precursor.

Film s w ere only attem pted w ithout hydrogen sulfide. This led to only tin(II) sulfide being deposited, although the precursor contained tin(IV). This is in accordance with observations m ade in Section 5.2.3.

Film s w ere deposited on tin oxide / silica coated glass. This m eant that accurate data from E D A X could not be obtained, although sulfur w as observed in the films. The m orphology o f the film s was dissim ilar to that observed using other precursors. Using a different substrate is an im portant factor in this observation.

5.5 Reactions

and

results

of

alkyl

tin