- Email: [email protected]
Efficiency of the secondary emission from a (001) Ag surface
Vacuum 68 (2003) 297–301
Efficiency of the secondary emission from a ð0 0 1Þ Ag surface Jerzy J. Czy’zewski*, Janusz Krajniak Institute of Experimental Physics, Wroc!aw University, pl. M. Borna 9, 50-204 Wroc!aw, Poland Received 16 April 2002; received in revised form 3 June 2002
Abstract The true secondary-electron-emission efficiency from an Agð0 0 1Þ surface in a take-off direction of 42:301 has been measured as a function of the primary electron energy, Ep : Applied procedure of the measurement and the processing data have related the true secondary-emission to the factor which includes the contribution of the primary current and the overall backscattering fraction. The measurements cover the energy range of Ep from 160 to 600 eV: r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Silver; Ag; Secondary electron emission; Electron-backscattering process
1. Introduction In experimental methods where an electron beam bombards a sample, electron-backscattering effects may take part in the generation of surface phenomena. Within the range of low primaryelectron energies, Ep ; the contribution of the backscattering fraction to the Auger electron (AE) generation factor has become the subject of theoretical and experimental studies [1–5] to estimate the necessary corrections which should be applied for quantitative analysis of the surface. Also, in the case of electron stimulated desorption (ESD) the backscattered electrons may make a contribution. Thus, the core-hole Auger decay mechanism of ESD may be stimulated both by the primary and the backscattered electrons if their energies are high enough to ionize the specific core
*Corresponding author. Tel.: +48-71-37592-15; fax: +4871-32873-65. E-mail address: [email protected] (J.J. Czy’zewski).
level. In particular, a backscattering correction seems to be meaningful in the case of Oþ ion electron stimulated desorption from O/Ag [6,7] and H2 O=Ag [8,9] adsorption systems. In general, the true secondary-electron-emission (TSEE) efficiency takes into account the contribution to the backscattered low-energy electron excitations at the bombarded surface. The main measurements in this work include the electron-backscattering spectra, NðE; Epk Þ taken as a function of the primary electron energy from a clean Agð0 0 1Þ surface.
2. Experimental details In detail, the experimental procedure has been already described in Ref. [5]. It is itemized briefly as follows: *
After the cleaning procedure of the Agð0 0 1Þ surface [5], the AE spectra were taken at
0042-207X/03/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 2 - 2 0 7 X ( 0 2 ) 0 0 4 6 1 - X
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
298 0.4
Ep = 1000 eV N(E) [nA ] *
*
x5
0.2
*
value. The corresponding set of the current values, Icr ; was measured in an electronic circuit connected to the crystal. Before a set of NðE; Epk Þ measurements was made the sample was heated at a temperature T ¼ 950 K for 1 min: A computer-automated system controlled the measurements of the NðE; Epk Þ curves. However, before a kth curve was measured the system was set to the parameters suitable to observe the kth elastic peak and, eventually, some necessary adjustment could be made before the start of each spectrum performance. At the end of the measurements the channeltron multiplication value was measured in a CMA detection system.
3. Results and discussion
0 150
200
250
300
350
400
450
Energy E [eV]
Fig. 1. AES spectrum of a Agð0 0 1Þ sample measured at Ep ¼ 1000 eV:
*
Ep ¼ 1000 eV: A strong AES peak was observed for silver at E AES ¼ 350 eV; as shown in Fig. 1, and this was used to calibrate the energy coordinate, E; for all the energy distribution curves, NðE; Epk Þ; measured as a function of Ep [10]. Our Cylindrical Mirror Analyser (CMA) was adjusted to values of Epk ; which were set in 20 eV steps from 160 to 600 eV: The criterion used for operation was to obtain the maximum height of the elastic peak and the minimum of its half-width. As a result the parameters of the gun focusing and the exact positions of the elastic peaks were stored in a computer file for use by a computer-automated system. At the end of this operation the thermo-emission current, I0 ; of the gun was adjusted to get the elastic peak heights equal to 1 nA for each Epk
A typical set of the electron energy distribution curves, NðE; Epk Þ is presented in Fig. 2 within the range of energy E from 6 to 75 eV: On the basis of the measured set, the TSEE efficiency has been calculated. The parameters suitable for the geometry of the CMA and applied to our calculations are shown in Fig. 3. The total primary electron current, I0 was controlled by direct measurement of the current Icr passing from the crystal via an electrometer to the ground. The current I0 ðEp Þ depends on Icr ðEp Þ as follows: I0 ðEp Þ sðEp ÞI0 ðEp Þ ¼ Icr ðEp Þ;
ð1Þ
where values of the Secondary Electron Emission coefficient s ¼ sðEp Þ were taken from the experimental results presented by Bronstein and Fraiman [11]. Taking into account the assumption that the total backscattered current, sðEp ÞI0 ðEp Þ; within the solid angle equal to 2p could be described by means of a cosine distribution with respect to the horizontal angle a; we may express the current Iin ðEp Þ; accepted by the input slit of the CMA as follows: Z 1 1 ð2Þ Iin D sI0 cosðaÞ dOD sI0 O cosða0 Þ; 2p 2p O
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
299
or Nin (E)
O cosða0 Þ s Icr ðEp Þ: ð3Þ 2p 1s The input current, Iin ðEp Þ; is expressed by the current Icr ðEp Þ; which can be directly measured and by the angle a0 which can be calculated from the focusing condition of the CMA electron-optics system [12–15]. The angle a0 is equal to 42:31 in the case of our CMA. On the other hand the input current, Iin ðEp Þ; can be expressed by analyzer transmission function, TðEÞ; the input energy distribution, Nin ðEÞ; and the output energy distribution Nout ðEÞ as follows: Z Ep Z Ep Nout dE: ð4Þ Nin ðEÞ dE ¼ TðEÞ 0 0 Iin D
Ep=160 eV
0
180 eV 200 eV 200 eV 240 eV 260 eV 280 eV 300 eV 320 eV 340 eV 380 eV 380 eV 400 eV 420 eV 440 eV 460 eV 480 eV 500 eV 520 eV 540 eV 560 eV 580 eV 600 eV 0
25
50
According to the theory of the CMA analyzer we have TðEÞ ¼ kE:
75
Energy E [eV] Fig. 2. A typical set of the electron energy distribution curves Nin ðEÞ measured as a function of the primary electron energy, within the range of Ep from 160 to 600 eV for Agð0 0 1Þ in a take-off direction of 42:301:
ð5Þ
Also, taking into account the channeltron multiplication g and the energy distribution NðEÞ which is directly measured by the CMA detection systems, we may express the transmission coefficient, k; by the following equation: R Ep 0 ðNðEÞ=EÞ dE k¼ : ð6Þ gO cosða0 Þ=2p s=ð1 sÞ Icr ðEp Þ On the basis of the last equation we have measured the value of k for our CMA instrument
Fig. 3. Schematic diagram of CMA showing the geometric parameters of the electron beam passing through an analyzer, which were used in the data processing.
300
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
taking: Ep ¼ 600 eV; O=2p ¼ 0:1408; s600 eV ¼ 1:604; a0 ¼ 42:31 and Icr600 eV ¼ 53 nA: As a result we have k ¼ 1:015 104 :
ð7Þ
The value of k does not depend on Ep ; [12–15], thus it can be applied to all energy distribution curves measured as a function of Ep : Z Ep Z Ep NðE; Ep Þ dE : ð8Þ Nin ðE; Ep Þ dE ¼ gkE 0 0 On the other hand, to be able to formulate a definition of SE efficiency [3] we need to define the effective fraction of the primary electron current, I0eff ; which can be done on the basis of Eq. (3): O cosða0 Þ I0 ðEp Þ: ð9Þ 2p Then, the efficiency can be related to the factor 0 ZaSE ; which includes both the effective fraction of the primary current, I0eff ðEp Þ and overall backscattering fraction as follows: ! R Ep eff a0 0 ðNðE; Ep Þ=gkEÞ dE ZSE ðEp Þ ¼ I0 ðEp Þ 1 þ : I0eff ðEp Þ
I0eff ðEp Þ ¼
ð10Þ Finally, the following definition of the true a0 ðEp Þ; has been secondary-emission efficiency, JSE formulated: R Ef SE ðE; Ep Þ=gkEÞ dE E ðN a0 JSE ðEp Þ ¼ i : ð11Þ ZSE ðEp Þ Processing our experimental data presented in Fig. 2 on the basis of Eqs. (10)–(11), the value of a0 Ef was varied. In Fig. 4, three curves of JSE ðEp Þ 1 2 calculated for: Ef ¼ 25 eV; Ef ¼ 35 eV and Ef3 ¼ 45 eV are presented. One may see there that the a0 TSEE efficiency JSE ðEp Þ shows its maximum and minimum at the same values of Ep in each of the three curves, though the efficiency itself increases if bigger values of Ef are taken. Thus, one may a0 observe that the function JSE ðEp Þ for the TSEE region of energy E from 6 eV to 25 eV has a minimum for Ep ¼ 266 eV and a small maximum for Ep ¼ 462 eV:
Fig. 4. The true secondary emission efficiency in a take-off a direction a0 ¼ 42:31 with respect to the surface normal, JSE0 ; calculated on the basis of the data presented in Fig. 2 and Eqs. (10) and (11) as a function of the primary electron energy Ep for varied parameter Ef :
If we consider the electron stimulated desorption (ESD) of the Oþ ions from the O–Ag and H2 O–Ag adsorption systems, the ionization of the core-hole to generate its oxygen-intra-atomic Auger decaying in ESD phenomenon would require just 24 eV: In this case the O ðL1 Þ oxygen core-level and two valence levels, i.e. O ðL23 Þ of 7 eV and O0 ðL23 Þ of 9 eV are involved [16]. According to Engelhardt and Menzel [6], the ESD cross section for the O–Ag adsorption system can be estimated to be of the order of 1020 : Thus, the Oþ signal of ESD was hardly detected and the choice of a value of Ep might be substantial. The same problem for ESD Oþ ions detected from the H2 O–Ag adsorption system was observed by Czy’zewski et al. [9].
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
301
4. Conclusions
Acknowledgements
The true secondary-electron-emission efficiency from an Agð0 0 1Þ surface in a takeoff direction of 42:301 has several extrema as a function of the primary electron energy, Ep : Consequences of this fact may be as follows:
This work was sponsored by the University of Wroc"aw in Poland under Grant No. 2016/UWr/ IFD/2001.
A quantitative comparison of two AE spectra within their low-energy range, if each of them was measured using both two different energy analyzers having specific geometry each and taking two different values of Ep ; requires calculation of the back-scattering correction, taking into account all the specific parameters for each analyzer as it has been shown in the case of the CMA. In the case of the electron stimulated desorption þ the function of the ion current, IESD vs. Ep ; may be affected by the contribution of the backscattering fraction to the ESD generation factor due to the core-hole Auger decay mechanism. Angular distribution of the backscattered electrons might be essential in this case, taking into account the relation of the inter-atomic Auger electron transitions to the specific directions of bonding towards a desorbed overlayer.
[1] Jab"onski A, Jansson C, Tougaard S. Phys Rev 1993;B 47:7420. [2] Jab"onski A, Powell CJ. Surf Sci 2000;463:29. [3] Ichimura S, Shimizu R. Surf Sci 1981;112:386. [4] Schmid R, Gaukler KH, Seiler H. In: Johari O, editor. Scanning electron microscopy, Vol. II. Chicago: SEM, 1983. p. 501. [5] Czyzewski JJ, Kaszczyszyn S, Krajniak J. Appl Surf Sci 2001;177:42. [6] Engelhardt HA, Menzel D. Surf Sci 1976;57:591. [7] Eickmans J, Otto A, Goldman A. Surf Sci 1985;149:293. [8] Fehlner FP, Mott NF. Oxidation Metals 1970;2(1):59. [9] Czy’zewski JJ, Krajniak J. Vacuum 1999;54:9. [10] Handbook of Auger electron spectroscopy. Eden Prairie, MN: Physical Electronics Ltd, 1995. p. 164. [11] Bronstein IM, Fraiman BS. Phys Solid State 1961;3:1188 [Fig. 1]. [12] Sar-el HZ. Rev Sci Instrum 1967;38:1210. [13] Hafner H, Simpson JA, Kuyatt CE. Rev Sci Instrum 1968;39:33. [14] Aksela S, Karras M, Pessa M, Suoninen E. Rev Sci Instrum 1970;41:351. [15] Gerlach RL. J Vac Sci Technol 1972;9:1043. [16] Knotek ML, Feibelman PJ. Phys Rev Lett 1978;40:964.
*
*
References
Efficiency of the secondary emission from a ð0 0 1Þ Ag surface Jerzy J. Czy’zewski*, Janusz Krajniak Institute of Experimental Physics, Wroc!aw University, pl. M. Borna 9, 50-204 Wroc!aw, Poland Received 16 April 2002; received in revised form 3 June 2002
Abstract The true secondary-electron-emission efficiency from an Agð0 0 1Þ surface in a take-off direction of 42:301 has been measured as a function of the primary electron energy, Ep : Applied procedure of the measurement and the processing data have related the true secondary-emission to the factor which includes the contribution of the primary current and the overall backscattering fraction. The measurements cover the energy range of Ep from 160 to 600 eV: r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Silver; Ag; Secondary electron emission; Electron-backscattering process
1. Introduction In experimental methods where an electron beam bombards a sample, electron-backscattering effects may take part in the generation of surface phenomena. Within the range of low primaryelectron energies, Ep ; the contribution of the backscattering fraction to the Auger electron (AE) generation factor has become the subject of theoretical and experimental studies [1–5] to estimate the necessary corrections which should be applied for quantitative analysis of the surface. Also, in the case of electron stimulated desorption (ESD) the backscattered electrons may make a contribution. Thus, the core-hole Auger decay mechanism of ESD may be stimulated both by the primary and the backscattered electrons if their energies are high enough to ionize the specific core
*Corresponding author. Tel.: +48-71-37592-15; fax: +4871-32873-65. E-mail address: [email protected] (J.J. Czy’zewski).
level. In particular, a backscattering correction seems to be meaningful in the case of Oþ ion electron stimulated desorption from O/Ag [6,7] and H2 O=Ag [8,9] adsorption systems. In general, the true secondary-electron-emission (TSEE) efficiency takes into account the contribution to the backscattered low-energy electron excitations at the bombarded surface. The main measurements in this work include the electron-backscattering spectra, NðE; Epk Þ taken as a function of the primary electron energy from a clean Agð0 0 1Þ surface.
2. Experimental details In detail, the experimental procedure has been already described in Ref. [5]. It is itemized briefly as follows: *
After the cleaning procedure of the Agð0 0 1Þ surface [5], the AE spectra were taken at
0042-207X/03/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 2 - 2 0 7 X ( 0 2 ) 0 0 4 6 1 - X
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
298 0.4
Ep = 1000 eV N(E) [nA ] *
*
x5
0.2
*
value. The corresponding set of the current values, Icr ; was measured in an electronic circuit connected to the crystal. Before a set of NðE; Epk Þ measurements was made the sample was heated at a temperature T ¼ 950 K for 1 min: A computer-automated system controlled the measurements of the NðE; Epk Þ curves. However, before a kth curve was measured the system was set to the parameters suitable to observe the kth elastic peak and, eventually, some necessary adjustment could be made before the start of each spectrum performance. At the end of the measurements the channeltron multiplication value was measured in a CMA detection system.
3. Results and discussion
0 150
200
250
300
350
400
450
Energy E [eV]
Fig. 1. AES spectrum of a Agð0 0 1Þ sample measured at Ep ¼ 1000 eV:
*
Ep ¼ 1000 eV: A strong AES peak was observed for silver at E AES ¼ 350 eV; as shown in Fig. 1, and this was used to calibrate the energy coordinate, E; for all the energy distribution curves, NðE; Epk Þ; measured as a function of Ep [10]. Our Cylindrical Mirror Analyser (CMA) was adjusted to values of Epk ; which were set in 20 eV steps from 160 to 600 eV: The criterion used for operation was to obtain the maximum height of the elastic peak and the minimum of its half-width. As a result the parameters of the gun focusing and the exact positions of the elastic peaks were stored in a computer file for use by a computer-automated system. At the end of this operation the thermo-emission current, I0 ; of the gun was adjusted to get the elastic peak heights equal to 1 nA for each Epk
A typical set of the electron energy distribution curves, NðE; Epk Þ is presented in Fig. 2 within the range of energy E from 6 to 75 eV: On the basis of the measured set, the TSEE efficiency has been calculated. The parameters suitable for the geometry of the CMA and applied to our calculations are shown in Fig. 3. The total primary electron current, I0 was controlled by direct measurement of the current Icr passing from the crystal via an electrometer to the ground. The current I0 ðEp Þ depends on Icr ðEp Þ as follows: I0 ðEp Þ sðEp ÞI0 ðEp Þ ¼ Icr ðEp Þ;
ð1Þ
where values of the Secondary Electron Emission coefficient s ¼ sðEp Þ were taken from the experimental results presented by Bronstein and Fraiman [11]. Taking into account the assumption that the total backscattered current, sðEp ÞI0 ðEp Þ; within the solid angle equal to 2p could be described by means of a cosine distribution with respect to the horizontal angle a; we may express the current Iin ðEp Þ; accepted by the input slit of the CMA as follows: Z 1 1 ð2Þ Iin D sI0 cosðaÞ dOD sI0 O cosða0 Þ; 2p 2p O
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
299
or Nin (E)
O cosða0 Þ s Icr ðEp Þ: ð3Þ 2p 1s The input current, Iin ðEp Þ; is expressed by the current Icr ðEp Þ; which can be directly measured and by the angle a0 which can be calculated from the focusing condition of the CMA electron-optics system [12–15]. The angle a0 is equal to 42:31 in the case of our CMA. On the other hand the input current, Iin ðEp Þ; can be expressed by analyzer transmission function, TðEÞ; the input energy distribution, Nin ðEÞ; and the output energy distribution Nout ðEÞ as follows: Z Ep Z Ep Nout dE: ð4Þ Nin ðEÞ dE ¼ TðEÞ 0 0 Iin D
Ep=160 eV
0
180 eV 200 eV 200 eV 240 eV 260 eV 280 eV 300 eV 320 eV 340 eV 380 eV 380 eV 400 eV 420 eV 440 eV 460 eV 480 eV 500 eV 520 eV 540 eV 560 eV 580 eV 600 eV 0
25
50
According to the theory of the CMA analyzer we have TðEÞ ¼ kE:
75
Energy E [eV] Fig. 2. A typical set of the electron energy distribution curves Nin ðEÞ measured as a function of the primary electron energy, within the range of Ep from 160 to 600 eV for Agð0 0 1Þ in a take-off direction of 42:301:
ð5Þ
Also, taking into account the channeltron multiplication g and the energy distribution NðEÞ which is directly measured by the CMA detection systems, we may express the transmission coefficient, k; by the following equation: R Ep 0 ðNðEÞ=EÞ dE k¼ : ð6Þ gO cosða0 Þ=2p s=ð1 sÞ Icr ðEp Þ On the basis of the last equation we have measured the value of k for our CMA instrument
Fig. 3. Schematic diagram of CMA showing the geometric parameters of the electron beam passing through an analyzer, which were used in the data processing.
300
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
taking: Ep ¼ 600 eV; O=2p ¼ 0:1408; s600 eV ¼ 1:604; a0 ¼ 42:31 and Icr600 eV ¼ 53 nA: As a result we have k ¼ 1:015 104 :
ð7Þ
The value of k does not depend on Ep ; [12–15], thus it can be applied to all energy distribution curves measured as a function of Ep : Z Ep Z Ep NðE; Ep Þ dE : ð8Þ Nin ðE; Ep Þ dE ¼ gkE 0 0 On the other hand, to be able to formulate a definition of SE efficiency [3] we need to define the effective fraction of the primary electron current, I0eff ; which can be done on the basis of Eq. (3): O cosða0 Þ I0 ðEp Þ: ð9Þ 2p Then, the efficiency can be related to the factor 0 ZaSE ; which includes both the effective fraction of the primary current, I0eff ðEp Þ and overall backscattering fraction as follows: ! R Ep eff a0 0 ðNðE; Ep Þ=gkEÞ dE ZSE ðEp Þ ¼ I0 ðEp Þ 1 þ : I0eff ðEp Þ
I0eff ðEp Þ ¼
ð10Þ Finally, the following definition of the true a0 ðEp Þ; has been secondary-emission efficiency, JSE formulated: R Ef SE ðE; Ep Þ=gkEÞ dE E ðN a0 JSE ðEp Þ ¼ i : ð11Þ ZSE ðEp Þ Processing our experimental data presented in Fig. 2 on the basis of Eqs. (10)–(11), the value of a0 Ef was varied. In Fig. 4, three curves of JSE ðEp Þ 1 2 calculated for: Ef ¼ 25 eV; Ef ¼ 35 eV and Ef3 ¼ 45 eV are presented. One may see there that the a0 TSEE efficiency JSE ðEp Þ shows its maximum and minimum at the same values of Ep in each of the three curves, though the efficiency itself increases if bigger values of Ef are taken. Thus, one may a0 observe that the function JSE ðEp Þ for the TSEE region of energy E from 6 eV to 25 eV has a minimum for Ep ¼ 266 eV and a small maximum for Ep ¼ 462 eV:
Fig. 4. The true secondary emission efficiency in a take-off a direction a0 ¼ 42:31 with respect to the surface normal, JSE0 ; calculated on the basis of the data presented in Fig. 2 and Eqs. (10) and (11) as a function of the primary electron energy Ep for varied parameter Ef :
If we consider the electron stimulated desorption (ESD) of the Oþ ions from the O–Ag and H2 O–Ag adsorption systems, the ionization of the core-hole to generate its oxygen-intra-atomic Auger decaying in ESD phenomenon would require just 24 eV: In this case the O ðL1 Þ oxygen core-level and two valence levels, i.e. O ðL23 Þ of 7 eV and O0 ðL23 Þ of 9 eV are involved [16]. According to Engelhardt and Menzel [6], the ESD cross section for the O–Ag adsorption system can be estimated to be of the order of 1020 : Thus, the Oþ signal of ESD was hardly detected and the choice of a value of Ep might be substantial. The same problem for ESD Oþ ions detected from the H2 O–Ag adsorption system was observed by Czy’zewski et al. [9].
J.J. Czy’zewski, J. Krajniak / Vacuum 68 (2003) 297–301
301
4. Conclusions
Acknowledgements
The true secondary-electron-emission efficiency from an Agð0 0 1Þ surface in a takeoff direction of 42:301 has several extrema as a function of the primary electron energy, Ep : Consequences of this fact may be as follows:
This work was sponsored by the University of Wroc"aw in Poland under Grant No. 2016/UWr/ IFD/2001.
A quantitative comparison of two AE spectra within their low-energy range, if each of them was measured using both two different energy analyzers having specific geometry each and taking two different values of Ep ; requires calculation of the back-scattering correction, taking into account all the specific parameters for each analyzer as it has been shown in the case of the CMA. In the case of the electron stimulated desorption þ the function of the ion current, IESD vs. Ep ; may be affected by the contribution of the backscattering fraction to the ESD generation factor due to the core-hole Auger decay mechanism. Angular distribution of the backscattered electrons might be essential in this case, taking into account the relation of the inter-atomic Auger electron transitions to the specific directions of bonding towards a desorbed overlayer.
[1] Jab"onski A, Jansson C, Tougaard S. Phys Rev 1993;B 47:7420. [2] Jab"onski A, Powell CJ. Surf Sci 2000;463:29. [3] Ichimura S, Shimizu R. Surf Sci 1981;112:386. [4] Schmid R, Gaukler KH, Seiler H. In: Johari O, editor. Scanning electron microscopy, Vol. II. Chicago: SEM, 1983. p. 501. [5] Czyzewski JJ, Kaszczyszyn S, Krajniak J. Appl Surf Sci 2001;177:42. [6] Engelhardt HA, Menzel D. Surf Sci 1976;57:591. [7] Eickmans J, Otto A, Goldman A. Surf Sci 1985;149:293. [8] Fehlner FP, Mott NF. Oxidation Metals 1970;2(1):59. [9] Czy’zewski JJ, Krajniak J. Vacuum 1999;54:9. [10] Handbook of Auger electron spectroscopy. Eden Prairie, MN: Physical Electronics Ltd, 1995. p. 164. [11] Bronstein IM, Fraiman BS. Phys Solid State 1961;3:1188 [Fig. 1]. [12] Sar-el HZ. Rev Sci Instrum 1967;38:1210. [13] Hafner H, Simpson JA, Kuyatt CE. Rev Sci Instrum 1968;39:33. [14] Aksela S, Karras M, Pessa M, Suoninen E. Rev Sci Instrum 1970;41:351. [15] Gerlach RL. J Vac Sci Technol 1972;9:1043. [16] Knotek ML, Feibelman PJ. Phys Rev Lett 1978;40:964.
*
*
References