Attestation of magnetron sputtered films as mass standards is presented. Homogeneous, long-lived
metal films were measured by different methods for comparison. The accuracy of the order 1 ng was found
to be provided by application of the metal film standards for element analysis by X-ray fluorescent method.
Keywords: Thin Films, Nano-Standards, Magnetron Sputtering, X-ray Reflectometry, X-ray Fluorescent
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3516

Baturin, A.A.

Borisova, S.S.

Bugaev, Ye.A.

Mikhailov, A.I.

Mikhailov, I.F.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 1, 01NTF17(3pp) (2013) 
 
 
2304-1862/2013/2(1)01NTF17(3) 01NTF17-1  2013 Sumy State University 
Metal Films as Mass Standard Samples in the Nano-Gram Range  
 
I.F. Mikhailov, A.A. Baturin, Ye.A. Bugaev, A.I. Mikhailov, S.S. Borisova 
 
National Technical University “Kharkov Polytechnical Institute”, 21 Frunze str, Kharkov, Ukraine 61002 
 
(Received 30 May 2013; published online 01 September 2013) 
 
Attestation of magnetron sputtered films as mass standards is presented. Homogeneous, long-lived 
metal films were measured by different methods for comparison. The accuracy of the order 1 ng was found 
to be provided by application of the metal film standards for element analysis by X-ray fluorescent method.  
 
Keywords: Thin Films, Nano-Standards, Magnetron Sputtering, X-ray Reflectometry, X-ray Fluorescent 
Method. 
 
 PACS number: 07.85.Nc 
 
1. INTRODUCTION 
 
Modern nano-technologies deal with extra-small el-
ement contents, thus determining requirements to the 
measurement methods. Using X-ray geometry with 
secondary target it is possible to increase the sensitivi-
ty of X-ray fluorescent analysis [1, 2]. But to reveal and 
measure element trace impurities in the bulk materi-
als, special mass standards are necessary to apply. 
Usually for measuring trace impurities, various diluted 
solutions are used as mass standards. However, the 
main drawback of such mixtures is inhomogeneity, so, 
their application is limited. Other techniques for 
standard sample preparation described in [3]. 
The developed technology of X-ray mirrors [4, 6, 7] 
allows preparing metal nano-layers which remain sta-
ble for a long time, thus, such objects may be used as 
mass standards for nano-trace measurements. Magne-
tron sputtered super-thin (of the order of 1 nm) extra-
smooth layers on substrates are analyzed by X-ray re-
flectivity method [4, 5] in order to determine film 
thickness (d) and density ( ). Thus, by ρ х d value the 
mass of film substance can be measured with high ac-
curacy (3-5%).  
The present work is purposed to studying thin film 
mass standards in the nano-gram range. 
  
2. SAMPLES AND INVESTIGATON METHODS 
 
DC magnetron sputtered cobalt films deposited onto 
silicon substrates were analyzed. The preparation pro-
cedure is described in details in [6]. The deposition was 
carried out in cycle manner. 500 cycles of deposition 
corresponded to film thickness near 20 nm. The sam-
ples were covered by 2 nm amorphous carbon layer to 
protect oxidation.  
X-ray fluorescent (XRF) analysis was carried out us-
ing the energy-dispersive spectrometer SPRUT-K (AO 
Ukrrentgen, Ukraine) with Si(Li) Х-100 detector 
(Amptek, USA) in the arrangement with a Ge second-
ary target. The shooting-through type Ag anode was 
used in the X-ray tube BS-22 in the regime U   35 kV, 
I  250 m, and exposure time 300 s. The optic scheme 
aperture was 8 10-6 (tube anode – irradiator, irradiator 
– sample, sample – detector). 
 he sample irradiated area was determined by the in-
tensity variation of Са-К  fluorescence line when the 2 
mm paper square moved relative to the sample-holder in 
vertical and horizontal directions with 1 mm step.  
The high homogeneity of the films allowed obtain-
ing mass standards less than 50ng using additional 
cutting the films. 
The values ρ х d  were determined by three differ-
ent methods: (i) by X-ray reflectivity oscillations [4, 5]; 
(ii) by XRF method measuring Со-К  line intensity [8]; 
and (iii) by film absorption of the substrate Si-K  fluo-
rescent signal [8].  
In the first case the cobalt mass was calculated as 
 
 500 0
500
n C n
H
M n S ,  (1) 
 
where H500 corresponds to Co thickness obtained for 500 
deposition cycles; Со is cobalt density; n is the number of 
deposition cycles; Sn  is the area of n-th sample. 
According to (1), the cobalt mass 53 ng was obtained 
for 7 deposition cycles at Sn = 0.28 cm2. Using a dia-
mond knife, the sample was cut into sections of 0.03, 
0.04, and 0.09 cm2.  
By the second method ρ х d value was determined 
as follows [8]:  
 
 
1
ln(1 )
sin sin
CoGe Co
dCo Co
Co
d
I
d
I
, (2) 
 
where GeCo  and  
Co
Co are, respectively, absorption mass 
coefficient of Ge-К  radiation of the secondary target, 
and one of the film Co-К  analytical line,  by cobalt;  
and  are, respectively, an incident angle of the sec-
ondary target radiation and the exit angle of fluores-
cent radiation recorded by detector; CodI  and 
Co
dI  are 
Со-К  analytical line intensities at d   and at “infi-
nite” thickness of the sample. 
Using the third method,   d value calculated by film 
absorption of the substrate Si-K  fluorescent signal [8]:  
 
 
1
0ln( )
sin sin
Ge Si Si
Co Co d
Si
d
I
d
I
, (3) 
 
where SiCo  is cobalt mass coefficient of absorption of the 
substrate analytical signal Si-K ; SidI   is the substrate 
Si-K  analytical line intensity with partial absorption 
of the radiation by the film; 0
Si
dI  is the intensity of the 
same line in the absence of the film.  
 I.F. MIKHAILOV, A.A. BATURIN, YE.A. BUGAEV PROC. NAP 2, 01NTF17 (2013) 
 
 
01NTF17-2 
3. RESULTS AND DISCUSSION 
 
In Fig.1, the dependences ρ  d on the cycle number 
obtained by the three methods described above are 
shown. The value ρ  d  13.44 10-6 g/cm2. was deter-
mined by X-ray reflectivity method (1) for the 16.8 nm 
sample. Almost the similar values we obtained the for 
 
 
 
Fig. 1 – d (g/cm2 10-6) values versus the number of deposi-
tion cycles for three independent methods: ( ) by X-ray reflec-
tivity oscillations; (■) by film fluorescence radiation intensity 
(Co-K  line); (□) by substrate fluorescence radiation intensity 
(Si-K  line) absorption. 
 
the same sample using other methods: 13.87 10-6 g/cm2 
– by the intensity of film fluorescent radiation (2 meth-
od); and 14.04 10-6 g/cm2 – by cobalt film absorption of 
the substrate fluorescent radiation (3 method) at rela-
tive inaccuracy not more than 2 .  The ρ х d plot ob-
tained by Eq. (2) is linear according to the linear de-
pendence „intensity – element mass‟ of fluorescent radi-
ation. As it is seen, the plot obtained by the 3 method 
gives a non-linear plot with higher values ρ  d than 
the previous one. This behavior we explain by the non-
planar  film surface in the beginning of the growth 
when  the coating is inhomogeneous and broken [5]. So,  
the model of substrate radiation absorption by the flat 
film is inadequate. As the whole substrate becomes 
completely coated by the film (after 500 cycles), the 
values ρ  d become similar for the three methods. 
The model used for calculation by (1) also considers 
the film as homogeneous over whole substrate surface. 
Therefore, for thicknesses less than 50 nm, we obtained 
overestimated mass values. As the second method is 
less sensitive to the coating inhomogeneity, we obtain 
reliable results in the whole range of thicknesses.  
Using the cobalt mass calculated by Eq. (1)  we built 
a calibration function of Со-К  fluorescence intensity 
versus Co film mass (Fig. 2).  
 
0
5
10
15
20
25
0 0,5 1 1,5 2
Mass, ng х 1000
In
te
n
s
it
y
, 
c
o
u
n
ts
 х
 1
0
0
0
 
 
Fig. 2 – A calibration function ”fluorescence intensity-film 
mass” in the range from 5 ng to 1800 ng 
 
The threshold of detectability for i-th sample is  
 
  min
3 i Bi
Ci
m I
m
I
,   
 
where IBi and ICi are integral intensities of back-
ground and analytical signals, respectively, and mi is 
cobalt mass in i-th sample. The  standard deviation 
2S for the calibration function (Fig. 2) scattering was 
8 ng. Thus, mass certification is possible in the range 
from 1 to 17 ng with accuracy about 1 ng according to 
the threshold of detectability, while in the range from 
17 to 1800 ng the accuracy is not worse than 8 ng.  
The film standards may by applied for any other 
element, but for Z  27, the accuracy decreases. For 
recalculation of the calibration function it is necessary 
to introduce a coefficient K [8]: 
 
 
1
1
qi Ge
i qi i
qi
i
qs Ge
s qs s
qs
S
S
K
S
S
 (4) 
 
where Sqi and Sqs are absorption jump values of for i-
th element and the standard, respectively; 
Ge
i and
Ge
s  are mass attenuation factors of the sec-
ondary target Ge-K  radiation by i-th element and the 
standard, respectively; qi and qs  are fluorescence 
yields of i-th element and the standard; i and s are 
densities of i-th element and the standard, respective-
ly.  
 
 
 
 
 METAL FILMS AS MASS STANDARD SAMPLES … PROC. NAP 2, 01NTF17 (2013) 
 
 
01NTF17-3 
4. CONCLUSIONS 
 
The magnetron sputtered metal layers onto single-
crystalline substrates are super-smooth, homogeneous, 
high stable and may be certified using different meth-
ods. So, these are promising mass standards in the 
wide nano-gram range (1 1800 ng). In the range from 1 
to 17 ng, the accuracy is about 1 ng, and in the range 
from 17 to 1800 ng it is not worse than 8 ng.   
In comparison of obtained Co film standards  with 
for water solution State Standards, the firsts showed 
the advantages of high stability and homogeneity at  
good accordance of calibration functions.  
 
 
 
REFERENCES 
 
1. M.G. Vasin, Yu.V. Ignatyev, A.E. Lakhtikov, 
A.P. Morovov, V.V. Nazarov, L.I. Trakhtenberg, X-Ray 
Spectrometry. 36, 270 (2007).  
2. I.F. Mikhailov, A.A. Baturin, A.I. Mikhailov, S.S. Borisova, 
Functional Materials, 18, 2 C. 150-155 (2011).  
3. J. Injuk., R. Van Grieken, A. Blank, Handbook of Practical 
X-Ray Fluorescence Analysis. Ch. 6: Specimen Preparation. 
(Springer Verlag: Berlin: 2006). 
4. E. Spiller, Soft X-ray Optics (SPIE: Bellingham, Washing-
ton: 1994).  
5. I.F. Mikhailov, S.S. Borisova, L.P. Fomina, I.N. Babenko, 
N.N. Melnik, F.A. Pudonin, SPIE “X-Ray Optics and Sur-
face Science” 2453, 186 (1995). 
6. Ye.A. Bugaev, A.Yu. Devizenko, E.N. Zubarev, V.V. Kondratenko 
Functional Materials 14, (4) 573 (2007). 
7. I.A. Artyukhov, A.V. Vinogradov, Ye.А. Bugayev, 
А.Yu. Devizenko, V.V. Kondratenko, Yu.S. Kasyanov, 
Zhurnal Eksperimentalnoy i Teoreticheskoy Fisiki, 136, 
1009 (2009) [in Russian].  
8. V.P. Afonin, N.I. Komyak, V.P. Nikolayev, R.I. Plotnikov, 
X-ray fluorescent analysis. (Ed. by N.F. Losev) (Nauka: 
Novosibirsk: 1991). 
9. I.F. Mikhailov, A.A. Baturin, A.I. Mikhailov, 
Ye.A. Bugayev, Pribory i tehnika eksperimenta, 1, 95(2013) 
[in Russian]. 
 


English

Metal Films as Mass Standard Samples in the Nano-Gram Range

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 1, 01NTF17(3pp) (2013)   2304-1862/2013/2(1)01NTF17(3) 01NTF17-1  2013 Sumy State University Metal Films as Mass Standard Samples in the Nano-Gram Range   I.F. Mikhailov, A.A. Baturin, Ye.A. Bugaev, A.I. Mikhailov, S.S. Borisova  National Technical University “Kharkov Polytechnical Institute”, 21 Frunze str, Kharkov, Ukraine 61002  (Received 30 May 2013; published online 01 September 2013)  Attestation of magnetron sputtered films as mass standards is presented. Homogeneous, long-lived metal films were measured by different methods for comparison. The accuracy of the order 1 ng was found to be provided by application of the metal film standards for element analysis by X-ray fluorescent method.   Keywords: Thin Films, Nano-Standards, Magnetron Sputtering, X-ray Reflectometry, X-ray Fluorescent Method.   PACS number: 07.85.Nc  1. INTRODUCTION  Modern nano-technologies deal with extra-small el-ement contents, thus determining requirements to the measurement methods. Using X-ray geometry with secondary target it is possible to increase the sensitivi-ty of X-ray fluorescent analysis [1, 2]. But to reveal and measure element trace impurities in the bulk materi-als, special mass standards are necessary to apply. Usually for measuring trace impurities, various diluted solutions are used as mass standards. However, the main drawback of such mixtures is inhomogeneity, so, their application is limited. Other techniques for standard sample preparation described in [3]. The developed technology of X-ray mirrors [4, 6, 7] allows preparing metal nano-layers which remain sta-ble for a long time, thus, such objects may be used as mass standards for nano-trace measurements. Magne-tron sputtered super-thin (of the order of 1 nm) extra-smooth layers on substrates are analyzed by X-ray re-flectivity method [4, 5] in order to determine film thickness (d) and density ( ). Thus, by ρ х d value the mass of film substance can be measured with high ac-curacy (3-5%).  The present work is purposed to studying thin film mass standards in the nano-gram range.   2. SAMPLES AND INVESTIGATON METHODS  DC magnetron sputtered cobalt films deposited onto silicon substrates were analyzed. The preparation pro-cedure is described in details in [6]. The deposition was carried out in cycle manner. 500 cycles of deposition corresponded to film thickness near 20 nm. The sam-ples were covered by 2 nm amorphous carbon layer to protect oxidation.  X-ray fluorescent (XRF) analysis was carried out us-ing the energy-dispersive spectrometer SPRUT-K (AO Ukrrentgen, Ukraine) with Si(Li) Х-100 detector (Amptek, USA) in the arrangement with a Ge second-ary target. The shooting-through type Ag anode was used in the X-ray tube BS-22 in the regime U   35 kV, I  250 m, and exposure time 300 s. The optic scheme aperture was 8 10-6 (tube anode – irradiator, irradiator – sample, sample – detector).  he sample irradiated area was determined by the in-tensity variation of Са-К  fluorescence line when the 2 mm paper square moved relative to the sample-holder in vertical and horizontal directions with 1 mm step.  The high homogeneity of the films allowed obtain-ing mass standards less than 50ng using additional cutting the films. The values ρ х d  were determined by three differ-ent methods: (i) by X-ray reflectivity oscillations [4, 5]; (ii) by XRF method measuring Со-К  line intensity [8]; and (iii) by film absorption of the substrate Si-K  fluo-rescent signal [8].  In the first case the cobalt mass was calculated as   500 0500n C nHM n S ,  (1)  where H500 corresponds to Co thickness obtained for 500 deposition cycles; Со is cobalt density; n is the number of deposition cycles; Sn  is the area of n-th sample. According to (1), the cobalt mass 53 ng was obtained for 7 deposition cycles at Sn = 0.28 cm2. Using a dia-mond knife, the sample was cut into sections of 0.03, 0.04, and 0.09 cm2.  By the second method ρ х d value was determined as follows [8]:    1ln(1 )sin sinCoGe CodCo CoCodIdI, (2)  where GeCo  and  CoCo are, respectively, absorption mass coefficient of Ge-К  radiation of the secondary target, and one of the film Co-К  analytical line,  by cobalt;  and  are, respectively, an incident angle of the sec-ondary target radiation and the exit angle of fluores-cent radiation recorded by detector; CodI  and CodI  are Со-К  analytical line intensities at d   and at “infi-nite” thickness of the sample. Using the third method,   d value calculated by film absorption of the substrate Si-K  fluorescent signal [8]:    10ln( )sin sinGe Si SiCo Co dSidIdI, (3)  where SiCo  is cobalt mass coefficient of absorption of the substrate analytical signal Si-K ; SidI   is the substrate Si-K  analytical line intensity with partial absorption of the radiation by the film; 0SidI  is the intensity of the same line in the absence of the film.   I.F. MIKHAILOV, A.A. BATURIN, YE.A. BUGAEV PROC. NAP 2, 01NTF17 (2013)   01NTF17-2 3. RESULTS AND DISCUSSION  In Fig.1, the dependences ρ  d on the cycle number obtained by the three methods described above are shown. The value ρ  d  13.44 10-6 g/cm2. was deter-mined by X-ray reflectivity method (1) for the 16.8 nm sample. Almost the similar values we obtained the for    Fig. 1 – d (g/cm2 10-6) values versus the number of deposi-tion cycles for three independent methods: ( ) by X-ray reflec-tivity oscillations; (■) by film fluorescence radiation intensity (Co-K  line); (□) by substrate fluorescence radiation intensity (Si-K  line) absorption.  the same sample using other methods: 13.87 10-6 g/cm2 – by the intensity of film fluorescent radiation (2 meth-od); and 14.04 10-6 g/cm2 – by cobalt film absorption of the substrate fluorescent radiation (3 method) at rela-tive inaccuracy not more than 2 .  The ρ х d plot ob-tained by Eq. (2) is linear according to the linear de-pendence „intensity – element mass‟ of fluorescent radi-ation. As it is seen, the plot obtained by the 3 method gives a non-linear plot with higher values ρ  d than the previous one. This behavior we explain by the non-planar  film surface in the beginning of the growth when  the coating is inhomogeneous and broken [5]. So,  the model of substrate radiation absorption by the flat film is inadequate. As the whole substrate becomes completely coated by the film (after 500 cycles), the values ρ  d become similar for the three methods. The model used for calculation by (1) also considers the film as homogeneous over whole substrate surface. Therefore, for thicknesses less than 50 nm, we obtained overestimated mass values. As the second method is less sensitive to the coating inhomogeneity, we obtain reliable results in the whole range of thicknesses.  Using the cobalt mass calculated by Eq. (1)  we built a calibration function of Со-К  fluorescence intensity versus Co film mass (Fig. 2).   05101520250 0,5 1 1,5 2Mass, ng х 1000Intensity, counts х 1000  Fig. 2 – A calibration function ”fluorescence intensity-film mass” in the range from 5 ng to 1800 ng  The threshold of detectability for i-th sample is     min3 i BiCim ImI,    where IBi and ICi are integral intensities of back-ground and analytical signals, respectively, and mi is cobalt mass in i-th sample. The  standard deviation 2S for the calibration function (Fig. 2) scattering was 8 ng. Thus, mass certification is possible in the range from 1 to 17 ng with accuracy about 1 ng according to the threshold of detectability, while in the range from 17 to 1800 ng the accuracy is not worse than 8 ng.  The film standards may by applied for any other element, but for Z  27, the accuracy decreases. For recalculation of the calibration function it is necessary to introduce a coefficient K [8]:   11qi Gei qi iqiiqs Ges qs sqsSSKSS (4)  where Sqi and Sqs are absorption jump values of for i-th element and the standard, respectively; Gei andGes  are mass attenuation factors of the sec-ondary target Ge-K  radiation by i-th element and the standard, respectively; qi and qs  are fluorescence yields of i-th element and the standard; i and s are densities of i-th element and the standard, respective-ly.       METAL FILMS AS MASS STANDARD SAMPLES … PROC. NAP 2, 01NTF17 (2013)   01NTF17-3 4. CONCLUSIONS  The magnetron sputtered metal layers onto single-crystalline substrates are super-smooth, homogeneous, high stable and may be certified using different meth-ods. So, these are promising mass standards in the wide nano-gram range (1 1800 ng). In the range from 1 to 17 ng, the accuracy is about 1 ng, and in the range from 17 to 1800 ng it is not worse than 8 ng.   In comparison of obtained Co film standards  with for water solution State Standards, the firsts showed the advantages of high stability and homogeneity at  good accordance of calibration functions.     REFERENCES  1. M.G. Vasin, Yu.V. Ignatyev, A.E. Lakhtikov, A.P. Morovov, V.V. Nazarov, L.I. Trakhtenberg, X-Ray Spectrometry. 36, 270 (2007).  2. I.F. Mikhailov, A.A. Baturin, A.I. Mikhailov, S.S. Borisova, Functional Materials, 18, 2 C. 150-155 (2011).  3. J. Injuk., R. Van Grieken, A. Blank, Handbook of Practical X-Ray Fluorescence Analysis. Ch. 6: Specimen Preparation. (Springer Verlag: Berlin: 2006). 4. E. Spiller, Soft X-ray Optics (SPIE: Bellingham, Washing-ton: 1994).  5. I.F. Mikhailov, S.S. Borisova, L.P. Fomina, I.N. Babenko, N.N. Melnik, F.A. Pudonin, SPIE “X-Ray Optics and Sur-face Science” 2453, 186 (1995). 6. Ye.A. Bugaev, A.Yu. Devizenko, E.N. Zubarev, V.V. Kondratenko Functional Materials 14, (4) 573 (2007). 7. I.A. Artyukhov, A.V. Vinogradov, Ye.А. Bugayev, А.Yu. Devizenko, V.V. Kondratenko, Yu.S. Kasyanov, Zhurnal Eksperimentalnoy i Teoreticheskoy Fisiki, 136, 1009 (2009) [in Russian].  8. V.P. Afonin, N.I. Komyak, V.P. Nikolayev, R.I. Plotnikov, X-ray fluorescent analysis. (Ed. by N.F. Losev) (Nauka: Novosibirsk: 1991). 9. I.F. Mikhailov, A.A. Baturin, A.I. Mikhailov, Ye.A. Bugayev, Pribory i tehnika eksperimenta, 1, 95(2013) [in Russian].  

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Metal Films as Mass Standard Samples in the Nano-Gram Range

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