S uc u al and Mechanical p ope ies o Ti–Si–C–ON
o biomedical applica ions
F eddy Guima ães
a
, C is ina Oli ei a
a
, Elsa Sequei os
a
, Ma a To es
a
, M. Susano
b
,
M. Hen iques
b
, R. Oli ei a
b
, R. Escoba Galindo
c
, S. Ca alho
a,
⁎,
N.M.G. Pa ei a
d
,F.Vaz
a
, A. Ca alei o
d
a
Dep . Física, Uni e sidade do Minho, Campus de Azu ém, 4800-058 Guima ães, Po ugal
b
IBB—Ins i u e o Bio echnology and Bioenginee ing Cen e o Biological Enginee ing, Uni e sidade do Minho, Campus de Gual a , 4700-057, Po ugal
c
Ins i u o de Ciencia de Ma e iales de Mad id (ICMM-CSIC), Can oblanco, 28049, Mad id, Spain
d
ICEMS—Fac. de Ciências e Tecnologia da Uni e sidade de Coimb a, 3030-788 Coimb a, Po ugal
A ailable online 4 Sep embe 2007
Abs ac
Ti–Si–C–ON ilms we e deposi ed by DC eac i e magne on spu e ing using di e en pa ial p essu e o oxygen (p
O2
) and ni ogen (p
N2
)
a io. Composi ional analysis e ealed he exis ence o wo di e en g ow h zones o he ilms; one zone deposi ed unde low p
O2
/p
N2
and ano he
zone deposi ed unde high p
O2
/p
N2
. The ilms p oduced unde low p
O2
/p
N2
we e deposi ed a a lowe a e and p esen ed a cc s uc u e, as well as,
dense and ea u eless mo phologies. The ilms deposi ed wi h high p
O2
/p
N2,
consequen ly highe oxygen con en , we e deposi ed a a highe a e
and de eloped an amo phous s uc u e. The s uc u al changes a e consis en wi h he ha dness and Young's modulus e olu ion, as seen by he
signi ican educ ion o he ha dness and in luence on he Young's modulus by inc easing p
O2
/p
N2.
© 2007 Else ie B.V. All igh s ese ed.
Keywo ds: Ti–Si–C–ON; Mechanical; S uc u al; Bioma e ials
1. In oduc ion
Signi ican de elopmen o nano echnology in ma e ial
science and enginee ing has aken place in he las decade.
The ecen in e es in he so-called mul i unc ional-coa ing
ma e ials is o majo impo ance, om bo h he undamen al
scien i ic iewpoin and in e ms o indus ial applica ions.
Mo e speci ically nowadays, as he endency in implan science
is o subs i u e he o al hip eplacemen , usually a a ie y o
ma e ials, such as me als, ce amics, polyme s and composi es
by ma e ials coa ed wi h p o ec i e hin- ilms [1]. Clinical
esul s show ha excessi e wea and wea deb is a e he
p ima y cause o ailu e implan s o ul a high molecula weigh
polye hylene—UHMWPE o me al [2]. Mo eo e , in ec ions
caused by commensal mic o ganisms a e also a cause o implan
ailu e. Fo example, S aphylococcus epide midis and o he
coagulase-nega i e s aphylococci (CoNS) a e amongs he
majo culp i s o hese in ec ions [3,4]. This is ela ed, in
pa , o hei abili y o adhe e o implan ed medical de ices and
o m bio ilms. Despi e se e al e o s o ind medical he apies
o ea bio ilm in ec ions [5], he physical emo al o an
in ec ed medical de ice is o en necessa y wi h i s associa ed
incon enience and addi ional economic cos . The e is conside -
able in e es in inc easing he li e ime o implan s h ough he
inhibi ion o bio ilm o ma ion and he use o mo e wea -
esis an biocompa ible coa ings.
The pu pose o his wo k is o s a o in es iga e he
easibili y o a ious Ti–Si–C–ON ilms o load-bea ing
medical de ices. F om known esul s i is widely accep ed ha
is possible o achie e supe ha dness by Si inco po a ion in TiN
[6] and a dec ease in he Young's modulus is obse ed by
addi ion o oxygen [7]. Also, wo k has shown ha he co osion
esis ance ends o be sligh ly imp o ed by oxygen inco po a-
ion [8]. Recen published wo ks showed ha Ti–Si–Cisa
p omising sys em because o i s pa icula s uc u e, as well as,
i s ex ao dina y mechanical and ibological p ope ies [9].
A
ailable online a www.sciencedi ec .com
Su ace & Coa ings Technology 202 (2008) 2403–2407
www.else ie .com/loca e/su coa
⁎Co esponding au ho .
E-mail add ess: [email p o ec ed] (S. Ca alho).
0257-8972/$ - see on ma e © 2007 Else ie B.V. All igh s ese ed.
doi:10.1016/j.su coa .2007.08.056
Taking his in o conside a ion, he main ask o his pape is
ocussed on he s udy o he s uc u al and mechanical
p ope ies o Ti–Si–C–ON ilms wi h di e en O/N a ios.
2. Expe imen al de ails
The Ti–Si–C–ON samples we e deposi ed by d.c. eac i e
magne on spu e ing om wo opposed high pu i y (99.6%) Ti
a ge s (20×10 cm
2
); one Ti a ge wi h some inc us ed Si
pelle s (he ea e designa ed as he TiSi a ge ) and he o he
wi h ca bon pelle s (designa ed as he TiC a ge ), placed in
p e e en ial e oded zone. The a ea occupied by he pelle s was
close o 11 cm
2
in each a ge . Deposi ions we e ca ied ou
unde an A +(N
2
+O
2
) a mosphe e in an Alca el SCM 650
appa a us. Du ing he deposi ions he subs a es (s eel and
silicon) we e o a ed 70 mm abo e he a ge a cons an speed
o 7 pm. The base p essu e in he chambe was abou 10
−4
Pa
and ose 4.5× 10
−1
Pa du ing he deposi ions.
In o de o change he amoun o oxygen, he samples we e
g own wi h a a ia ion in he N
2
+O
2
low (changing he N
2
om 6.5 o 0 sccm and he O
2
om 0 o 5.25 sccm), while
main aining he A low cons an a 60 sccm. The subs a e bias
ol age and he empe a u e we e kep cons an a −50 V and
200 °C, espec i ely. The cu en densi y applied o he TiC
a ge was 5 mA/cm
2
and ha o he TiSi a ge was 6 mA/cm
2
.
Elec on P obe Mic oAnalysis (EMPA) and Glow Discha ge
Op ical Emission Spec oscopy (GDOES) we e used o he
de e mina ion o he chemical composi ion o he coa ings
and we e ca ied ou using a Cameca SX-50 elec on p obe
mic oanalysis appa a us and a Jobin Y on RF GD P o ile ,
espec i ely. The c oss-sec ional mo phology was examined
using a con en ional SEM on ac u ed samples. The s uc u e
and phase composi ion o he coa ings we e assessed by XRD,
using a con en ional Philips PW 1710 di ac ome e , ope a ing
wi h CuK
α
adia ion, in a B agg-B en ano con igu a ion. The
ha dness (H) and he Young's modulus (E), we e e alua ed by
dep h-sensing inden a ion, using a Fishe scope H100 appa a us
a maximum load o 30 mN. Co ec ion o he geome ical
de ec s in he ip o he inden e , he mal d i o he equipmen
and unce ain y o he ini ial con ac was also pe o med in
ag eemen wi h wha is p oposed on [10,11]. I should be
poin ed ou ha any co ec ion due o esidual s esses was
done. The Residual s esses, σ
, we e ob ained by he de lec ion
me hod om S oney's equa ion [12], using subs a e cu a u e
adii, bo h be o e and a e coa ing deposi ion [13].
3. Resul s and discussion
3.1. Composi ion mo phology analysis
The chemical analysis o he ilms was ob ained using
GDOES and EPMA measu emen s. Fo he deposi ed samples
he esul s o an a e age o hese analyses as unc ion o he
oxygen pa ial p essu e and he ni ogen pa ial p essu e a io
(p
O2
/p
N2
) a e shown in Fig. 1. I is isible ha he Si and C
con en emains almos cons an o all coa ings independen o
p
O2
/p
N2
and he alue is e y low (b10 a .%). As expec ed, he
ni ogen con en dec eased om 54 o 2 a . % and he oxygen
inc eased om 2.9 o 34.7 a . % on inc easing he p
O2
/p
N2
om
0.046 o 20. Also an inc ease in Ti con en was obse ed as p
O2
/
p
N2
inc eased. In ac , due o he high amoun o ni ogen in he
coa ing deposi ed wi h lowe p
O2
/p
N2
(NN50 a .%), i is
possible ha he a ge s a e al eady poisoned; his would also
explain he low deposi ion a e o his coa ing (as can be seen in
Fig. 2). By inc easing he oxygen low, he oxygen beha iou
is no linea , o lowe low a es dissocia ion o he oxy-
gen molecules can occu , which inc eases he eac i i y o
he sys em and hus he deposi ion a e (seen in Fig. 2). A
he same ime some ni ogen a oms a e eplaced by oxygen
(p
O2
/p
N2
=0.6) and in a second phase, he eac ion be ween he
oxygen in he a ge commences. This eac ion s a s in a
monolaye o med by chemiso p ion and o each oxygen a om
inco po a ed in he a ge , wo o ni ogen a e eed, due o he
o ma ion o a TiN laye o he o ma ion o a TiO
2
laye . This
will inc ease he pa ial p essu e o ni ogen in he eac i e
a mosphe e, which can explain he lowe oxygen con en o he
coa ing deposi ed a p
O2
/p
N2
=0.8, keeping in mind ha , he
low o eac i e gas is always he same and so, he numbe o
molecules o O
2
+N
2
is cons an . To educe oxygen poisoning,
Fig. 1. Va ia ion o he concen a ion o Ti, C, Si, O and N as a unc ion o p
O2
/
p
N2
.
Fig. 2. Va ia ion o he deposi ion a e as a unc ion o p
O2
/p
N2
.
2404 F. Guima ães e al. / Su ace & Coa ings Technology 202 (2008) 2403–2407
i is equi ed o double he numbe o a oms in compa ison o
ha o ni ogen. This will inc ease o he non-poisoned ac ion
o he a ge , acco ding he Be g's Model, and should inc ease
in he numbe o he spu e ed Ti a oms, leading o an inc ease in
Ti composi ion. Fo he coa ings deposi ed wi h a high p
O2
/p
N2
a io, he con inua ion o he p e iously desc ibed phenomenon
occu s, bu because o he dec ease o he ni ogen low, he
amoun o ni ogen in he coa ing educes, while a he same
ime he oxygen low is inc eased, which will p omo e an
inc ease o he oxygen in he coa ing. The amoun o oxygen
added o he eac i e a mosphe e is no enough o each he
s oichiome ic composi ion TiO
2
, see composi ion o he
coa ing deposi ed wi h p
O2
/p
N2
=20, his is an e idence o a
non-poisoned a ge , du ing he deposi ion wi h high amoun o
oxygen, and his is he explana ion o he high deposi ion a e
o his coa ing, as is seen in Fig. 2.
The mo phology o he coa ings is disclosed by c oss-sec ional
SEM mic og aphs o ac u ed samples, shown in Fig. 3.
Conside ing he esul s o samples ep esen ing he g oup
deposi ed wi h low p
O2
/p
N2
(Fig. 3a), all ilms show dense and
e y compac ea u eless mo phologies. The dec ease in he
deposi ion a e can induce his compac mo phology. The
mic os uc u e o single-phase ilms is quali a i ely well
desc ibed by he s uc u al zone models de eloped by Mo chan
and Demchishin [14] and Tho n on [15]. These models, howe e ,
change ma kedly when impu i ies o selec ed addi i es a e
inco po a ed in he ilms [16]. Impu i ies o addi i es (like oxygen
in ou case) s op he g ain g ow h and s imula e a enuclea ion o
g ains, which esul s in a globula mo phology. The sample
deposi ed wi h p
O2
/p
N2
=1.76 (Fig. 3b) p esen s his ype o
mo phology. As he p
O2
/p
N2
is u he inc eased he coa ings
p esen mo phologies wi h a la ge numbe o oids wi hin shaped
c ys alli es (Fig. 3c), as a esul o he highe deposi ion a e.
3.2. S uc u e cha ac e iza ion
The di e ences in he composi ion a e well co ela ed wi h he
di e ences obse ed in he de eloped s uc u e. The X- ay
di ac og ams o he as-deposi ed samples a e illus a ed in
Fig. 4. In e na ional Cen e o Di ac ion Da a (ICDD) o α—Ti
(ICDD ca d n . 44-1294), TiN (ICDD ca d n . 38-1420,
TiC (ICDD ca d n . 01-071-6256), and TiC
0.2
N
0.8
(ICDD ca d
n . 01-076-2484) we e also included a he op o Fig. 4.The
abo e-men ioned egimes changes (low p
O2
/p
N2
a io and high
p
O2
/p
N2
a io) a e also e iden in he s uc u al ea u es e ealed
by he XRD esul s. Fo he samples deposi ed unde low p
O2
/p
N2
i is possible o iden i y a cc ype s uc u e and he e is a endency
o an inc ease in he peak in ensi y a io I
(111)
/(I
(111)
+I
(200)
wi h
inc ease in p
O2
/p
N2
, indica ing a p e e en ial c ys alline g ow h
change. I is di icul o unequi ocally iden i y which phases a e
o med. E.V. Shalae a e al. [17] s a ed o Ti–Si–N–O ilms
ha a a silicon con en o 10 a . %, he ilms had nea ly single-
phase c ys alline s uc u e TiSiN(O) wi h minimum g ain size
1.5–2 nm. Al hough, a ha momen , wi h he di ac ion analysis,
he e is no e idence ha silicon is pa ially dissol ed in a cubic
solid solu ion TiSiN(O). Ca bon and oxygen subs i u ion o
egula ni ogen posi ions o o med cc Ti(C,O,N) phase, once
he ni ogen con en dec eases, could be possible. The samples
ha we e deposi ed a high p
O2
/p
N2
p esen ed a signi ican loss o
c ys allini y, wi h he sample wi h highes oxygen con en ound
o be amo phous. Fo his g oup he inc ease in he deposi ion a e
(as men ioned be o e) and he a ailable oxygen ha is in-
co po a ed in he la ice, educes he possibili y o c ys alliza ion.
The ex ended de o ma ion o he cc s uc u e esul ing om he
Fig. 3. C oss-sec ional mic og aphs o Ti–Si–C–ON coa ings o di e en p
O2
/p
N2
a) 0.046 b) 1.73 c) 20.
Fig. 4. XRD pa e ns o di e en Ti–Si–C–ON ilms.
2405F. Guima ães e al. / Su ace & Coa ings Technology 202 (2008) 2403–2407
inco po a ion o oxygen p obably inc eases he numbe o
de ec s, which acili a es he o ma ion o he amo phous
s uc u e. The obse ed changes in ilm s uc u e and o ien a ion
as a unc ion o p
O2
/p
N2
, can be desc ibed in h ee s eps:
- Fi s a low p
O2
/p
N2
, he oxygen is p obably inco po a ed
in o he g ain bounda ies and con inues o accumula e du ing
GB mig a ion, esul ing in a ex u e wi h low deg ee o
p e e ed o ien a ion and wi h low g ain size (Fig. 4);
- Second wi h sligh ly highe p
O2
/p
N2
coa sening du ing
coalescence is se e ely supp essed. The compe i i e g ow h
which ollows is go e ned by aniso opic c ys allog aphic
e ec s since he oxygen is inco po a ed in o he la ice, as
desc ibed in [18]. The ilm is composed o globula g ains
(Fig. 3b) wi h andom o ien a ion (Fig. 4);
- Thi d as he p
O2
/p
N2
is u he inc eased, wi h inc easing
oxygen concen a ion, he g ain size dec eased. The p esence
o oxide phases inhibi s GB mig a ion in he bulk o he ilm,
p e en ing g ain coa sening, becoming he ilm g ow h, a
e y high p
O2
/p
N2
, amo phous.
3.3. Mechanical p ope ies
The e olu ion o ha dness and Young's modulus as a
unc ion o he p
O2
/p
N2
is illus a ed in Fig. 5. The s uc u al
changes a e consis en wi h he e olu ion o he ha dness, as i
can be seen by he signi ican educ ion o he ha dness by
inc easing p
O2
/p
N2
, a ying om ypical TiN (23 GPa) ilm o
he lowes p
O2
/p
N2
o hose o TiO
x
amo phous phase o
highes concen a ion o oxygen (≈15 GPa) [19]. The eplace-
men o ni ogen by ca bon a oms and he addi ion o Si in he
coa ings leads o a dis o ion in he NaCl la ice ype s uc u e,
which usually esul s in he inc ease o ha dness [20,21]. This is
no obse ed in ou coa ings p obably due o he amoun o
oxygen, as i is known ha he oxygen ac ing as an impu i y
dec eases he ha dness o he coa ings [22]. A isible dec ease
in Young's modulus was ound, wi h inc easing p
O2
/p
N2
and ela es o an inc ease on he de ec densi y and also he
dec ease o he bonding ene gy, due o he inc ease dis ance
be ween he a oms Ti, N and O, as he s uc u e changes o an
amo phous ype.
Fig. 6 shows he e olu ion o esidual s ess as unc ion o
p
O2
/p
N2
. F om his g aph i is clea ha all coa ings a e in he
comp essi e s ess s a e. This esul should be expec ed because
o he low wo king p essu e (b0.45 Pa). Unde hese condi ions,
spu e ed a oms o e lec ed A neu als could induce he well-
known a omic peening e ec , which p omo es he comp essi e
esidual s ess s a e [12,23]. Rega ding he e olu ion o he
comp essi e s esses wi h inc easing p
O2
/p
N2
, i is possible o
see ha he e is a dependence o he esidual s ess on he p
O2
/
p
N2
. I is also no iceable a co ela ion be ween he comp essi e
s esses and he measu ed ha dness. Fi s he ha des samples
(deposi ed wi h low p
O2
/p
N2
) p esen ed he highes esidual
s ess alues, which we belie e is due o ilm densi ica ion and
he p esence o la ice de ec s in he ilm's s uc u e, which ac
as an obs acle o disloca ion mo ion. Secondly, o he ilms
deposi ed wi h a high p
O2
/p
N2
which p esen ed e y low
ha dness alues and de eloped a po ous columna g ow h is
obse ed a s ong endency o s ess educ ion. Fu he mo e, as
he oxygen inc eases he dis o ion in he c ys alline la ice
inc eases, leading o a endency o ilm o become amo phous,
as can be seen om he di ac ion pa e ns. As a esul o his
highe deg ee o amo phous s uc u e, he ilms enhance hei
capaci y o accommoda e he s ess, leading o a educ ion o
i s alue. Fo he highes oxygen con en , eached o highes
p
O2
/p
N2
, he coa ing is amo phous and he e o e he esidual
s esses and ha dness a e e y low. In he li e a u e, Pa ei a
e al. [12] as well as Vaz e al. [19] ha e s udied he in luence
o he oxygen ac ion in he esidual s esses and ha dness o
W–O–N, Ti–O–N coa ings, espec i ely. Globally, also hei
case, he ha dness and esidual s ess dec eased wi h inc easing
oxygen ac ion.
4. Conclusions
Ti–Si–C–ON hin ilms we e deposi ed by eac i e mag-
ne on spu e ing wi h di e en p
O2
/p
N2
. The ilms deposi ed
unde low p
O2
/p
N2
p esen ed a dense and compac mo phology,
a cc—c is alline s uc u e, ha dness highe han 20 GPa, highe
Fig. 6. Comp essi e esidual s esses o spu e ed Ti–Si–C–ON as a unc ion o
p
O2
/p
N2
.
Fig. 5. Ha dness o spu e ed Ti–Si–C–ON as a unc ion o p
O2
/p
N2
.
2406 F. Guima ães e al. / Su ace & Coa ings Technology 202 (2008) 2403–2407
comp essi e esidual s ess. The ilms ha we e deposi ed
wi h highe p
O2
/p
N2
p esen ed a po ous mo phology and a e
amo phous. These samples exhibi ed low ha dness and e y low
comp essi e esidual s ess. Tanking accoun he applica ion
o hese coa ings (biomedical applica ion), p elimina y esul s
showed, ha samples deposi ed wi h highe a ios o p
O2
/p
N2
p esen ed lowe alues o bio ilm o ma ion, indica ing ha he
inc ease o oxygen leads o bioma e ials less suscep ible o be
colonized by S. epide midis. Howe e , hese bioassays will be
p esen ed by he au ho s in a u u e publica ion.
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