Investigation by EELS and TRIM simulation method of the interaction of Ar and N ions with the InP compound

In this study, the EELS results revealed the great sensitivity of InP compound submitted to Ar⁺ or N⁺ ions at low energy. The preliminary treatment of InP by the Ar⁺ ions was useful as part of the cleaning process of the surface. Further argon ions bombardment on cleaned InP led however to breaking of chemical bonds In–P, with desorption of phosphorus atoms and appearance of In metal distributed on InP. The damaged InP by Ar⁺ ions, constituted the diphase (In; InP) system of depth of about 30 Å, involving a superficial roughness. The In metal proportion on such a system was determined by a calculation method based on the experimental EELS spectra of pure In and InP.We submitted the heated and no heated system (In; InP) to nitrogen ions bombardment. The nitrogen reacted with the In metal to compensate the phosphorus vacancies so that InN species were formed. The heating of (In; InP) system at 450 °C, allowed the surface reconstruction with elimination of defects due to the structure and the roughness. The temperature also caused the coalescence of In metal towards the surface. Because of the physical stability of the interface of heated (In; InP) system, the nitrogen reacted with the outmost layers of In metal to form a homogeneous layer of InN of thickness estimated at 20 Å. We associated to the EELS the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction Ar⁺ or N⁺ ions-InP and determine the disturbed depth as a function of the energy. The EELS alone was not able to give us with accuracy the disturbed depth of the target by these ions.     

Determination of the inelastic mean free path of electrons in GaAs and InP after surface cleaning by ion bombardment using elastic peak electron spectroscopy

The inelastic mean free path (IMFP) of electrons is an important material parameter needed for quantitative AES, EELS and non-destructive depth profiling. The distinction between the terms for IMFP and the attenuation length (AL) has been established by ASTM standards. A practical experimental method for determining values of the IMFP is elastic peak electron spectroscopy (EPES). In this method, experimentally determined ratios of elastically backscattered electrons from test surfaces and from a Ni reference standard are compared with the values evaluated theoretically.The present paper reports systematic measurements of the IMFP by EPES for GaAs and InP. They are carried out in two laboratories using two different electron spectrometers: a CMA in Budapest and DCMA in Warsaw. Prior to measurements, the samples were amorphized by high-energy Ar⁺ ions (100–400 keV), and the surface composition was determined by quantitative XPS. Argon cleaning produces enrichment of samples in the surface layer in Ga (80%) and In (70%), respectively. The experiments refer to a such modified sample surface that was considered in Monte Carlo calculations. The experimental data were analyzed using calibration curves from Monte Carlo calculations which account for multiple elastic scattering events. This approach has been used previously for elemental solids and is now extended to amorphized binary compounds. The experimental values of IMFP obtained in both laboratories exhibited a reasonable agreement with the available literature data in the 0.1–3.0 keV energy range. With respect to the information depth of EPES, the experimental results refer to the bulk composition within a reasonable extent.     

Ar+, He+，S+离子轰击n-InP单晶表面的机理研究

通过X射线光电子能谱和低能电子衍射实验研究了10～180 eV的Ar⁺、 He⁺、S⁺离子轰击n-InP(100)表面, 发现S⁺离子轰击可以产生In-S组分,减轻离子轰击对表面的物理损伤.对于Ar⁺离子轰击后的表面,经过S⁺离子处理和加热过程以后,表面损伤得到了修复,最终得到了2×2的InP表面,进一步验证了S⁺离子对InP表面的修复作用.     

Ultraviolet photoelectron spectroscopy of nano In clusters Schottky barriers on sputtered InP

Plasmon peaks along with Auger P_LVV peak have been observed in the ultraviolet photoelectron spectra (UPSs) of InP after 5 min of sputtering with 0.5 kV Ar⁺ ions. Plasmon and Auger peaks are not observed in UPS of un-sputtered InP surface with native oxides of In and P. Filled electron energy levels are not observed near the Fermi level from 5 min sputtered InP surface due to increase of ionization potential of nano In clusters.     

Effect of ion bombardment at low energy on (100)InP surfaces,studied by Auger electron spectroscopy

Surface cleaning of (100)InP substrates with an Ar⁺ ion beam of 250–400 eV is analysed by AES and shown as a function of time. The results obtained show the possibility of removing the contamination layer without any significant chemical damage to the InP surface.     

Electron irradiation effect on the surface composition of Ar+ ion bombarded Si-nitride and Si-oxinitride

Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) have been used to study the surface composition of the Si-nitride and Si-oxinitride prepared by low pressure chemical vapor deposition. Ion bombardment has been shown to result in appearance of the “free” silicon on the surface. Electron irradiation of the samples preliminary bombarded by Ar⁺ ions has led to disappearance of the “free” silicon. This process is assumed to be connected with electron stimulated desorption of the “free” silicon.     

AES analysis of nitridation of Si(100) by 2–10 keV N+2 ion beams

Ion beam nitridation of Si(100) as a function of N⁺₂ ion energy in the range of 2–10 keV has been investigated by in-situ Auger electron spectroscopy (AES) analysis and Ar⁺ depth profiling. The AES measurements show that the nitride films formed by 4–10 keV N⁺₂ ion bombardment are relatively uniform and have a composition of near stoichiometric silicon nitride (Si₃N₄), but that formed by 2 keV N⁺₂ ion bombardment is N-rich on the film surface. Formation of the surface N-rich film by 2 keV N⁺₂ ion bombardment can be attributed to radiation-enhanced diffusion of interstitial N atoms and a lower self-sputtering yield. AES depth profile measurements indicate that the thicknesses of nitride films appear to increase with ion energy in the range from 2 to 10 keV and the rate of increase of film thickness is most rapid in the 4–10 keV range. The nitridation reaction process which differs from that of low-energy (< 1 keV) N⁺₂ ion bombardment is explained in terms of ion implantation, physical sputtering, chemical reaction and radiation-enhanced diffusion of interstitial N atoms.     

Investigation on surface compositions of CuNi alloy under Ar+ ion bombardment by ISS and in situ AES measurements

Surface compositions of CuNi(50 wt%) alloy under 3 keV Ar⁺ ion bombardment were measured by Auger electron spectroscopy (AES) and ion scattering spectroscopy (ISS). In situ AES measurement of sputter-deposited layer and sputtered sample surface indicated that surface composition became Ni-rich due to Ar⁺ ion sputtering at steady state, in accord with previous reports of preferential sputtering. ISS measurements with 3 keV Ar⁺ ions, however, have suggested that the composition of the outermost atom layer is not Ni-rich but slightly copperrich. This leads to the conclusion that the degree of preferential sputtering is small and that the question of preferential sputtering, particularly, the ratio of the sputtering yields, $\text{S}{}_{\mathrm{<mtext>Cu</mtext>}}\text{S}{}_{\mathrm{<mtext>Ni</mtext>}}$, based on AES measurement requires further examination.     

Ar ion milling of InSb for manufacturing single electron devices

Ar⁺ ion milling of InSb for manufacturing single electron devices was studied. It is shown that pyramidal structures (porous) are created on the (1 1 1) surface of InSb wafers by anisotropic etching. Also it was shown the axis of the pyramidal structure is a function of the angle of the Ar⁺ incident beam and does not depend on the energy of the beam. EDX measurement results show In_xO_y and Sb_xO_y were not created on the surface after milling process. FTIR measurement results show that the surface reflection was decreased and less than 0.3 V flat band voltage was seen in capacitance voltage measurement results. SEM images show that the etching has approximately vertical profile. Therefore the Ar⁺ milling technique can be used as a dry etching technique for manufacturing mesa and/or porous structures of InSb. Since the surface is porous and of near-pyramidal morphology, one can simulate the surface by a set of needles each of which is a nanometer-size capacitance (i.e. single electron device). We showed, the threshold voltage of this single electron device is 0.3 V approximately, and therefore it can be used for studying single-electron or Coulomb blockade effects.     

Metastable Decomposition of Ar3+ Cluster Ions Into Ar2+ and Ar+

In this note we present the first account of a study of metastable (unimolecular decay) and collision-induced dissociation of Ar₃+ cluster ions using an experimental setup consisting of a molecular beam-electron impact ion source and a double focussing (reversed Nier Johnson geometry) mass spectrometer. The existence of the following metastable decay processes (accessible by our sampling time window) could be demonstrated: Ar₃⁺* → Ar₂+ and Ar₃⁺* → Ar⁺. The processes were studied as a function of electron impact energy. The present results are of importance in order to provide some guidance for the development of appropriate theoretical models for the dissociation of cluster ions.     

ISS measurement of surface composition of AuCu alloys by simultaneous ion bombardments with Ar+ and He + ions

Surface composition of Au-Cu(43 at%) alloy under 1.5–5 keV argon ion bombardment has been investigated by ion scattering spectroscopy (ISS). In this experiment, we adopted a specific technique to use mixed He⁺ and Ar⁺ ions as primary beam in order to perform sputtering (Ar⁺) and ISS measurement (He⁺) simultaneously. The outermost atom layer of Au-Cu alloys under Ar⁺ ion bombardment is Au-rich leading to the conclusion that Ar⁺ ion bombardment of AuCu alloys causes the preferential sputtering of Cu atoms, resulting in a Au-rich outermost atom layer and a depletion layer of Au atoms beneath the outermost atom layer due to ion-beam-enhanced surface segregation. This result explains the experimental results obtained by AES as well.     

Sputtering of A 3 B 5 materials (GaP, GaAs, GaSb, InP, and InSb) by 2-to 14-keV N 2 + ions

Investigations of the general characteristics and distinctive features of sputtering of A ³ B ⁵ materials (GaP, GaAs, GaSb, InP and InSb) under bombardment with N ₂ ⁺ ions have been carried out. From the experimental data, dependences of the sputtering yield of these materials on the incidence angle and ion energy have been obtained and the surface relief patterns produced by target etching have been studied. It has been shown that the dependence on energy of the sputtering yield for GaP, GaAs, and InP can be adequately described by the Haffa-Switkovski formula for binary materials and Yudin’s approximation for elemental targets. Sputtering of GaSb and InSb proceeds in the surface layer recrystallization mode, and the sputtering yield agrees with calculations based on Onderlinden’s model. From a comparison of the experimental and calculated dependences, the surface bonding energies have been determined.     

An upgraded TOF-SIMS VG Ionex IX23LS: Study on the negative secondary ion emission of III-V compound semiconductors with prior neutral cesium deposition

A TOF-SIMS VG Ionex IX23LS with upgraded data acquisition and control system was used to study the secondary emission of negative atomic and cluster ions of non-metallic elements (P, As and Sb) upon a 19 keV Ga⁺ bombardment of non-degenerated III-V semiconductors (GaP, GaAs, GaSb, InP, InAs and InSb) with prior neutral Cs deposition from a getter dispenser. It was found that surface cesiation enhances the peak intensity of all negative ion species; in the case of atomic ions, the greatest increase (360) was observed for P⁻ emitted from InP. Such an enhancement was larger for In-based than for Ga-based compounds. We explained that in terms of an electronegativity difference between the composing atoms of III-V semiconductors. The greater electronegativity difference (bond ionicity) of In-based compounds resulted in the greater Cs-induced work function decrease leading to a higher increase in the ionization probability of secondary ions.     

SEM and XPS studies of nanohole arrays on InP(1 0 0) surfaces created by coupling AAO templates and low energy Ar ion sputtering

The aim of the present study is to demonstrate the feasibility to form well-ordered nanoholes on InP(1 0 0) surfaces by low Ar⁺ ion sputtering process in UHV conditions from anodized aluminum oxide (AAO) templates. This process is a promising approach in creating ordered arrays of surface nanostructures with controllable size and morphology. To follow the Ar⁺ ion sputtering effects on the AAO/InP surfaces, X-ray photoelectron spectroscopy (XPS) was used to determine the different surface species. In_4d and P_2p core level spectra were recorded on different InP(1 0 0) surfaces after ions bombardment. XPS results showed the presence of metallic indium on both smooth InP(1 0 0) and AAO/InP(1 0 0) surfaces. Finally, we showed that this experiment led to the formation of metallic In dropplets about 10 nm in diameter on nanoholes patterned InP surface while the as-received InP(1 0 0) surface generated metallic In about 60 nm in diameter.     

AES depth profiling with N2+ ion sputtering

Depth profiling of a polycrystalline multicomponent film using AES was compared with Ar⁺ and N₂⁺ ion sputtering. The latter appears to give an improved depth resolution.     

An AES and ESCA study of GCr15 steel coated with Ti,Cr and bombarded by N+ and Ar+

GCr15 steel specimens coated with Ti, Cr and bombarded with N⁺, Ar⁺ were analyzed by AES and ESCA (PHI-550). The results show that (1) the specimens bombarded with N⁺ have improved surface mechanical properties compared to those bombarded with Ar⁺; (2) the changes in the surface properties are related to the composition of the surface layer, mainly to TiO₂, TiN, Cr₂O₃, and other compounds. Also, the presence of carbon is found to be advantageous in modifying GCr15 bearing steel.     

State-selective radiative recombination cross sections of argon ions

The n-, (n,l)- and fine-structure level state-selective radiative recombinations (RR) cross sections of argon ions Ar¹⁸⁺,Ar¹³⁺,Ar⁷⁺ and Ar⁺ are obtained with the semi-classical Kramer formula, the relativistic self-consistent field (RSCF) method and the relativistic configuration interaction (RCI) method. It is found that for the highly charged ions with few electrons, the cross sections calculated with these three methods are in good agreement with each other. But as the number of electrons increases, the Kramer formula deviates from the RSCF and RCI results. For instance, when the energy of the incident electron is larger than 100 eV, the n-state selective cross sections of Ar⁷⁺ calculated from the Kramer formula are underestimated for more than 50%. The RSCF results are in general agreement with the RCI results. However, for the low charged ions, a clear distinction appears due to the strong configuration interaction, especially near the Cooper minimum. The n-resolved (n≤10) and total Maxwellian averaged rate coefficients are calculated, and the analytic fitting parameters are also provided.     

Electron IMFPs in bulk Cd0.88Mn0.12Te crystals determined by EPES

The inelastic mean free path (IMFP) of electrons is a basic parameter for surface-sensitive electron spectroscopies (AES, XPS, EELS) in quantitative analyses.Cd_1−xMn_xTe mixed crystals are currently of great interest due to their magnetic and magneto-optical properties. Since information on electron transport processes in these semimagnetic compounds is scarce, their systematic studies are highly desirable.In the present work, the IMFPs in Cd_0.88Mn_0.12Te (1 1 0) crystal samples were obtained from EPES with use of the Ni standard in the electron energy range 500-2000 eV. In addition, we also explored the effect of bulk Mn content in the determination of the IMFP. Relative EPES measurements were carried out using the MICROLAB 350 spectrometer. The sample surface was sputter cleaned and amorphized by Ar⁺ ions. Surface composition of the samples was monitored in situ by XPS and AES. The measured IMFPs were uncorrected for surface excitations and compared with those predicted from the TPP-2M and G-1 formulae. Also, the values of the IMFPs determined here were compared with those evaluated from the expression of Sekine et al. However, accuracy of this expression is rather poor except the case of pure CdTe (x = 0). In general, good agreement was found between the measured IMFPs in Cd_0.88Mn_0.12Te and the corresponding predicted IMFPs. The root-mean-square deviation from IMFP values predicted from the TPP-2M formula was 1.2 Å. The mean percentage deviation from the TPP-2M IMFPs was 9.3%.     

Surface characteristics of V-Ga alloys after irradiation by Ar<Superscript>+</Superscript> and N<Superscript>+</Superscript> ions

V-5Ga-6Cr and V-5Ga-0.05Ce vanadium alloys irradiated by Ar⁺ and N⁺ ions with energies of 20 keV have been investigated. Irradiation by Ar⁺ and N⁺ ions leads to strengthening of the surface layers of samples. Their thicknesses exceed the projectile ranges of these ions (16.4 and 32.8 nm, respectively) in vanadium by more than two orders of magnitude. The experimentally determined penetration depth of argon ions is less that 70 nm. The sample side irradiated by Ar⁺ ions has a predominant orientation of crystallites in the (100) and (211) planes, while the unirradiated sample has a (110) surface. The lattice parameter of the irradiated sample does not differ from that of the initial sample. Possible mechanisms by which modified deep layers are formed during ion bombardment are discussed.     

Interplay of native defect-related photoluminescence response of ZnO nanosticks subjected to 80 keV Ar ion irradiation

We report on the effect of 80 keV Ar⁺ ion irradiation on the luminescence response of zinc oxide (ZnO) nanosticks synthesized using a simple microemulsion route. The formation of nanoscale rods was confirmed from the transmission electron microscopy, whereas the hexagonal wurtzite phase of the nanorods was detected in an X-ray diffraction pattern. The photoluminescence pattern of the nanorods was dominated by various native defect states of ZnO, which are responsible for the quenching of the typical band edge emission of ZnO. Under Ar⁺ ion irradiation at a fluence of 1×10¹³ ions/cm², the band edge emission was recovered owing to the suppression of oxygen vacancy defects. In addition, the formation of new zinc vacancy and ionized zinc interstitial defects were also evident. Conversely, the band edge emission was found to be quenched as a result of the creation of more oxygen vacancy (V_O) defects due to ion irradiation (fluence: 1×10¹⁵ ions/cm²). The nuclear energy loss of the Ar⁺ ions in ZnO is responsible for the formation of point (vacancy-related) defects, while relatively small amount of electronic energy loss of the Ar⁺ ion results in the ionization of the neutral zinc interstitial (Zn_i) defects. The energy deposition scheme of the energetic ions has been elaborated with the help of theoretical modeling that explains the observed features quite satisfactorily.