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Pal, Pinaki

Kumar, Krishna

The Effect of Magnetic Field on Wavy Roll Instability

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Dielectric Study of Particulate Material in e.m. Field at Microwave Frequencies

Indian J. Phys. 82 (8), 947-948 (2008) ^ ^ f c 
illlM) fflft 
Vol. 82 • No. 8 • August 2008 
I N T E N T S 
Special Issue on 80 years of the Discovery of Raman Effect 
& 175th Birth Anniversary of Dr. Mahendra Lai Sircar 
Front Title 941 
Advisory Board and Editors 943-944 
From Editor's Desk 945 
Front Contents 947-948 
Foreword 949 
Reprinted from Indian Journal of Physics Vol. II and Proceedings 
of the Indian Association for the Cultivation of Science Vol. XI 
VoL II, Part III (24) pp 387-398 (1927-1928) 
A New Radiation 
PROF. C V RAMAN, FRS 951-967 
The Discovery of the Raman Effect 
80 years ago - the Discovery of the Raman Effect at the Indian Association 
for the Cultivation of Science, Kolkata, India 
RAJINDER SINGH 969-985 
Raman optical activity : a novel version of chiroptical spectroscopy 
MOITRAYEE MUKHERJEE, ANAMIKA MUKHOPADHYAY AND TAPAS CHAKRABORTY .... 987-1001 
[ Cont'd, on next page ] 
948 Contents 
Cultivation of Science in the 19th Century Bengal 
RAJESH KOCHHAR 1003-1082 
Forthcoming Publications 1083 
Notes for Contributors 1085-1088 
Our Special Publications 1089-1090 


Front Contents

Singh, Rajinder

80 Years Ago - the Discovery of the Raman Effect at the Indian Association for the Cultivation of Science, Kolkata, India

Indian J. Phys. 81 (8), 837-838 (2007) 
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English

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Sahu, T

Indian J. Phys. 81(1) 17-23(2007) 
<3> 
Electron transport in barrier delta-doped coupled quantum 
well structures 
TSahu 
Department of Dectronic Science, Berhampur University, Berhampur-760 007, Orissa, India 
E-mail : tsahu_bu@rediffmail.com 
Abstract : In this invited talk, we briefly review the work done on low temperature electron subband mobility jun in various 
<?-doped systems. We then analyse //„ in double quantum well structures, which exhibits the tunneling coupling in addition to 
confinement effect. We discuss the importance of intersubband coupling on //„ in a multisubband system. The effect of 
screening of the scattering potentials by 20EG on subband electron mobility is also highlighted. 
Keywords : Electron mobility, delta doping , 2DEG . double quantum wells, GaAs/AIGaAs . GaAs/lnGaAs systems. 
PACSNo. : 72.10.-d 
1. Introduction 
The study of properties of two dimensional electron gas (2DEG) in semiconductor 
structures has been a subject of interest from both technological as well as fundamental 
point of view [1-4]. The invention of modulation doped heterostructures (MDH) [5,6], 
which afforded a physical separation of the electrons from the ionized parent donors, 
led to a realization of an exceedingly high electron mobility // of the 2DEG [7]. A new 
challenge thus emerged to understand the mechanism of electron transport [8] in the 
modulation doped heterostructures and also to explore the possibility of other systems 
exhibiting such properties. 
2. Delta-doped systems 
In recent years, attempts have been made to realize 2DEG by confining the distribution 
of dopant atoms over a very narrow width, ideally one-monolayer called ^-doping [9,10]. 
The confinement potential in the <?-doped systems is simply formed by the interaction 
between ionized impurities in the doping layer and the delocalised electrons around it. 
This gives rise to quantum size effect and therefore subband structures [1]. The <?-
doped systems are characterized by high electron density and usually more number of 
subbands are populated [9]. Several experimental investigations have also been made 
to study 2DEG and also electron transport in delta-doped systems both theoretically 
and experimentally. [11-18]. Gonzalez et al. [19] have calculated the low temperature 
© 2007 IACS 
18 TSahu 
electron mobility in tf-doped GaAs. They have considered a multisubband system and 
analysed the effect of screening of the ionised impurities on subband mobility. They 
have shown that the Random Phase approximation proves quite good in predicting 
subband mobility. However, their calculations were based on the assumption of an ideal 
zero thickness impurity layer. 
Hai et al [20-22] have made a study of electron transport properties of <S-doped 
semiconductor systems. They have obtained the subband electronic structure of Si 
delta-doped GaAs by solving the coupled Schrodinger equation and the Poisson's 
equation selfconsistently. The screening of the ionised impurity scattering potential by 
2DEG is taken into account through the static dielectric function within the Random 
Phase Approximation. The effect of intersubband scattering and screening on subband 
electron mobility has been investigated. Attempts have also taken to investigate 
electron mobility by increasing the number of delta-doped layers [23]. 
In addition to delta-doping in bulk materials, delta-doping in quantum wells (QWs) 
has attractive features in addition to confinement of the QWs [24-26]. 
3. Barrier delta-doped systems 
A great deal of interest has also been developed in the study of the advantages of & 
doping in the barrier region of heterostructures. Schubert et al, have demonstrated that 
in modulation doped structures the carrier mobility increases when the thickness of the 
doping layer is reduced and a peak value of // is achieved when the distribution of 
dopants has a ^-function like profile [27]. In modulation doped GaAs/A^Ga^xAs 
systems, the AlxGa^xAs layer uniformly doped with Si contains a large number of Dx 
centers, which cause instability in the device operation due to persistent photoconductivity 
effect [28]. It has been shown that the Dx centers can be reduced by replacing the 
uniformly doped AI^Ga^jAs layer by a Si - delta-doped layer [29]. Attempts have also 
been made to analyse the effect of barrier material on the 2DEG in delta-doped GalnAs 
based quantum well systems [30]. 
Hsu et al [31] have proposed a delta-doped GaAs/lnxGa^xAs/GaAs pseudomorphic 
structure which manifested high mobility and high 2DEG concentration. Here the GaAs 
barrier is delta-doped with Si. Subsequently Hsu et al [32] have fabricated highly 
strained delta- and uniformly-doped InP/lnGaAs/lnP high electron mobility transistor 
(HEMT) structure with InGaP cap layer. Attempts have also been made to improve the 
device performance [33,34]. 
A. Bebinski et a/. [35] have studied the transport and quantum electron mobility 
In modulation Si delta-doped pseudomorphic GaAs/lnGaAs/AIGaAs quantum wells. 
Huang et al [36] have investigated the subband properties of Si £doped pseudomorphic 
InGaAs/GaAs heterostructures by solving the Schrodinger-Kohn-Sham equation and the 
Poissons equation selfconsistently. They have considered different ^doping configurations 
by placing the ^doping layer at various positions with respect to InGaAs well. 
4. Double quantum well systems 
A double quantum well (DQW) structure provides an ideal system for studying tunneling 
dynamics [37]. The modulation doping of a coupled DQW creates two parallel 2DEG 
Electron transport in barrier delta-doped coupled quantum well structures 19 
layers which exhibits interesting properties [38,39]. When two wells are brought closer, 
mixing of subband wave functions occurs leading to splitting in the subband energy 
levels. By changing the material parameters such as wfll width, barrier width, doping 
concentration, etc. the subband energy levels can be varied and hence it is possible 
to obtain a system in which more than one subband can be occupied. Several 
attempts have been made to study the electronic structure, optical and transport 
properties of double quantum well structures [40-46]. 
Recently Sahu and Patnaik have studied the low temperature electron mobility fin 
in barrier delta-doped GaAs/AI^ Ga^^As double quantum ;well structures by considering 
ionised impurity scattering [43-44]. We have also considered GaAs/ln^a,^ As double 
quantum well systems [45]. Unlike the GaAs/A^Ga^^As systems, here the well region 
is the alloy layer (InGaAs). Hence one has to consider the effect of alloy disorder 
scattering in addition to the ionised impurity scattering. We analyse the effects of 
screening on the alloy disorder potential, which has been normally neglected due to its 
short range nature. It has been showed that the effect of intersubband coupling and 
screening of the scattering potentials are important in studying jin in a multisubband 
system. 
5. Subband electron mobility 
We shall discuss low temperature electron mobility /*„ limited by ionized impurity and 
alloy disorder scatterings [7]. The alloy disorder scattering is of short range in order 
and normally the effect of screening is neglected [47]. However, it is interesting to 
demonstrate the effects of screening and intersubband coupling on the alloy disorder 
scattering [45]. 
Using linear response theory [1] the screened potential Ve*(q) and the external 
impurity potential V(q) can be related through the inverse dielectric matrix e~ln<m>. 
Within random phase approximation (RPA) the dielectric matrix can be written as 
*nmtnm'(Q) « M « t f + <<fc ' Q^nnm^MZn^M ' 0 ) 
where qs =2meP/e0h2, F is the Coulomb form factor and x is *he static electron 
density- density correlation function without electron-electron interaction [1]. 
For a multisubband system the expressions for the subband transport life time 
rn satisfies a coupled linear equation and contains the intra-subband and inter-subband 
scattering processes in a mixed way [28,43-45]. For a single occupied band (n = 0) 
one can write 
f-*o. (2) 
For double occupied bands (n = 0,1) 
A , (fibo+Q>i)(fln-,-cio)-Q>ifio 
T
° ( 5 1 + C , 0 ) + ( £ F 1 / £ F O M I < 3 ) 
20 
TSahu 
i_ (EL,+Cn,)(31+C10)-q )^o 
Ti"(Soo + C 0 1 ) + ( ^ o / ^ D i o 
(4) 
The scattering rates Bnn, Cnm and Dnm are expressed in terms of the scattering matrix 
elements Vnm(q) as 
B„ = mf(ntP))d9Q-cas0)\v£ (qnnf , 
o 
Cnm = m/(nh3)]dO \\C(qnmf, 
0 
Dnm = m/(nh3)] dO cos0\V*(qnn (5) 
Cnm= Cmn and Dnm'= Dmn. Here *Fn = {2mEFfr andgn; « [ £ , + * * - 2 1 ^ *„cos0]^ . 
£pn = EF - E„. 
The screened ionized impurity potential and alloy disorder potentials are given by 
io^^][r> 
n'm* 
|vC(Q)f=[a3(^fx(1-x)/4] 
(6) 
(7) 
- W K / 2 f * 
- H ^ / 2 - w,, 
^ . • ( ^ • W C J o ) 
2
 w„/2+ivw 
+ J cfcrj 
* 6 /2 
S^nU)^mU)Cnm(Q) (8) 
where a is the lattice constant of the alloy layer, SV is the alloy scattering potential 
and * is the alloy fraction. The indices if and rrf run over all the subband levels. 
However, one has to limit the sum such as considering the filled levels. 
We have considered a double quantum well structure (symmetric about z « 0). 
The middle barrier is of width wb. The adjacent wells are of width w„. One can keep 
the £-doped layer at the centre of the structure (within the middle barrier) [43] or can 
place it in the side barriers [44,45] keeping the middle barrier undoped. The width of 
the Si delta-doped layer is kept constant d A The doping concentration is N0 cm*3. The 
electrons are transferred to the adjacent wells. Band bending occurs due to the 
Coulomb interaction and the alignment of the Fermi level (EF) throughout the system. 
This gives rise to symmetric triangular-like potential wells within the well layers. When 
the detta-doped layer lies within the central barrier, the triangular-like potential wells lie 
near the interfaces with the central barrier. Whereas, the delta-doping layer being in the 
side barriers, the triangular-like potential wells occur near the interfaces with the side 
Electron transport in barrier delta-doped coupled quantum well structures 21 
barriers. In any case, the electrons are confined to two narrow strips along the 
interface planes (xy-plane) forming two sheets of 2DE<$ [1] coupled through a thin 
central barrier, leading to quantization of the energy bfuids into subband structures 
along the growth direction (z-axis). 
The confinement potential V(z), the subband energy eigen values En and wave 
functions i/rn(z) need to be obtained numerically from a | selfconsistent solution of the 
coupled one-dimensional Schrodinger equation and the Pdpsson's equation. However, for 
sake of simplicity one can obtain an analytical expression for V{z) by solving the 
Poisson's equation by adopting variatiional trial wave function approach [1]. The bound 
subband energy levels En and wave functions y/n(z) are pumerically obtained by using 
multistep potential method [48]. 
6. Discussion 
The subband mobility of double quantum well systems have been elaborately studied 
by changing the well width, barrier width, doping concentration, etc. [43-45]. In the 
present invited paper we shall point out some salient features such as the effects of 
screening and intersubband coupling on the subband electron mobility. 
From the symmetry of the double quantum well structures and the properties of 
the form factor [43-45], we note that the intersubband terms C01 and D01 (eq. 5) remain 
almost unchanged compared to the unscreened values. Screening causes reduction in 
Bnn and hence enhances the subband mobility. Therefore the effect of screening is felt 
through the intrasubband scattering rate matrix elements B^ and B^ only. 
We shall now discuss the important aspects relating to intersubband coupling 
and screening of the scattering potentials on electron mobility jun. From eqs. 3 and 4 
we see that for a system with two-subband occupancy, the subband transport rate 1/:b 
and 1/r-, contains the intrasubband (B00 and B^ ) and intersubband (C0i and D01) terms 
in a mixed way, unlike that of a single subband system which contains a single term 
(eq. 2). Thus intersubband scattering affects the mobility through these additional 
terms. In addition, intersubband coupling also affects the intrasubband terms B00 and 
Bn through the dielectric matrix element occurring in the screened scattering potential 
V6fi(q) eq. (1) thus leading to change in mobility. 
Another important feature of intersubband scattering is the occurrence of sudden 
drop in subband mobility at the onset of occupation of a higher subband. We note that 
when the Fermi level is just above the second subband, eq. (3) reduces to 
- &oo + coi * 
Comparing the above equation with eq. (2), one can find that the drop in JUQ »S due 
to the contribution of additional intersubband terms C01. However, we note that at the 
onset of occupation of the second subband there is a discontinuity in the dielectric 
function matrix which also causes a sudden change in the intrasubband scattering rate 
Boo. Therefore the change in //0 te d u e t 0 t h e combination of both the effects. We have 
shown. [43,45] that for impurity scattering the drop in ti0 is mostly due to the sudden 
22 
7 Sato; 
change in fl^. Whereas, for alloy scattering there is no discontinuity in Bfln. The drop 
in Mo mostly due to the additional contributions of intersubband term C01. 
7. Conclusion 
In this invited talk we briefly review the work done on low temperature electron mobility 
in various £-doped semiconductor structures. We consider a double quantum well 
structures, which exhibits the tunneling coupling in addition to confinement effect. We 
have shown that in a multi subband system the subband electron mobility contains the 
intrasubband and intersubband scattering processes in a mixed way. We discuss the 
importance of intersubband coupling on electron mobility. The effect of screening of the 
scattering potentials by 2DEG on subband electron mobility is also discussed. The 
results can be utilized for device applications. 
References 
[1] T Ando, A B Fowler and F Stern Rev. Mod. Phys. 54 437 (1982) 
[2] E E Mendez and K Von Klitzing Physics and applications of quantum wells and superlatoces, (eds.) (New 
York: Plenum) (1987) 
[3] G Bastard Wave Mechanics Applied to Semiconductor Heterostructure ( New York : Halsted) (1988) 
[4] Weisbuch and B Vinter Quantum Semiconductor Structures (New York : Academic) (1991) 
[5] L Esakl and R Tsu IBM Research Laboratories, International Report No. RC 2418 1969 (unpublished) 
[6] R Dingle, H L Stormer, A C Gossard and W Wiegman Appl. Phys. Lett 33 665 (1978) 
[7] L Pfeiffer, K W West, H L Stormer and K W Balwin Appl. Phys. Lett. 55 1987 (1985) 
[8] B R Nag Electron Transport in Compound Semiconductors (New York . Springer Verlag) 
[9] K Ploog J. Crystal Growth 81 304 (1987) 
[10] E F Schubert (ed.) Delta-doping of Semiconductors (Cambridge : Cambridge University Press) (1995) 
[11] PM Koenraad, A C L Heessels, F A P Blom, J A A J Perenboom and J H Wolter Physica 8184 221 (1993) 
[12] I A Panaev, S A Studenikin, D I Lubyshev and V A Migal Semicond. Sci. Technol. 8 1822 (1993) 
[13] J J Harris, R Murray and C T Foxon Semicond. Sci. Technol. 8 31 (1993) 
[14] MH Degani Phys. Rev. B445580(1991) 
[15] E Ozturk, Y Ergun and H San and I Solmen J. Appl. Phys. 91 2118 (2002) 
[16] A Gold, A Ghajali and J Serre Semicond. Sci. Technol. 7 972 (1992) 
[17] L loriatti Phys. Rev. B41 8340 (1989) 
[18] O Mezrin and A Shik Superlatt. Microstruct. 10 107 (1991) 
[19] L R Gonzalez, J Krupski and T Szwacka Phy Rev. B49 11111 (1994) 
[20] G Q Hai, N Studart and F M Peeters Phy. Rev. B52 8363 (1995) 
[21] G Q Hai, and N Studart Phy. Rev. B52 R2245 (1995) 
[22] G K Hai, N Studart, F M Peeters, P M Koenraad and J H Wolter J. Appl. Phys. 80 5809 (1996) 
[23] G Q Hai and N Studart and F M Peeter Phys. Rev. 52 11273 (1995) 
[24] Y C Shih and B G Streetman Appl. Phy Lett. 59 1344 (1991) 
[25] G Q Hai and N Studart Phy. Rev. B55 6708 (1997) 
[26] M J Kao, W C Hsu, H M Shich, W C Liu and C Y Chang Jpn. J. Appl. Phys. 34 L1 (1995) 
|27] E F Schubert, L Pfeiffer, K W West and A Izabelle AppL Phys. Lett. 54 1350 (1989) 
[28] R Fletcher. E Zaramba, M D' lorio, C T Foxon and J J Harris Phy. Rev B41 10649 (1990) 
[29] J A Correa, A G de Oltoira, M I N da Silva, G M Ribeno and J F Sampaio J. Vac. Sci. Technol. B15 870 
Electron transport in barrier delta-doped coupled quantum well structures 23 
[30] I Lo, W C Mitchel, P W Yu, A Fathimulla and H Hier J. Appl. Phys. 79 9196 (1996) 
[31] W C H Su, C M Chen and W Lin J. Appl. Phys. 70 4332 (1991) 
[32] R T Hsu, W Lin, W C Hsu and J S Su Jpn. J. Appl. Phys. 33 6514 (1994) 
[33] Y Fu and M Willander J. Appl. Phys. 78 3504 (1995) 
[34] P L Souza, B Yavich, M Pamplana Pires, A B Herrigues and L C D Gojhclaves J. Appl. Phys. 821700 (1997) 
[35] A Babinski, J S Matuszyk, J M Baranowski, G Li and C Jagadish Afypt. Phys. Lett. 77 999 (2000) 
[36] 2 Huang, C Jiang, 2 2hang, T Lin, J Chu and R Yu J. Appl. Phys. 9# 3115 (2001) 
[37] R R Ferreira and G Bastard Rep. Prog. Phys. 60 345 (1997) 
[38] J P Eisenstein, G S Boebinger, L N Pfeiffer, K W West and S He Ptys. Rev. Lett. 68 1383 (1992) 
[39] R E Prange and S M Girvm (eds.) The Quantum Hall Effect (New York . Springer-Verlag) (1989) 
[40] I Lo, J K Tsai, P C Ho, W J You, C H Chang, J C Ching, Li W Ju, Q X 2uao Phys. Rev. B67 195317 (2003) 
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[44] T Sahu and J Patnaik Superlattices and Microstructures 30 119 (2001) 
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[48] Y Ando and T Itoh J. Appl. Phys 61 1497 (1987)

Electron Transport in Barrier Delta-Doped Coupled Quantum Well Structures

Rautray, T R

Mishra, Satrujit

Patnaik, S K

Vijayan, V

Panigrahi, S

Indian J. Phys. 81 (1) 99-102(2007) 
Analysis of human bone and teeth 
T R Rautray*1-4, Satrujit Mishra2, S K Patnaik3, V Vij^an4 and S Panigrahi1 
department of Physics, NIT, Rourkeia-769 008, Orissa, India 
2Department of Physics, Berhampur University, Berhampur-760 007, Orissa, India 
^Department of Dentistry, City Hospital, Berhampur-760 007, Orissa, India 
institute of Physics, Bhubaneswar-751 005, Orissa, India 
E-mail : tapashC i^opb res m 
Abstract : The trace element analysis of four human bone samples of an individual of age 54 who died of an accident, 
were collected from different parts (tibia, parietal and occipital bone) of the human body by autopsy and analysed by particle 
induced X-ray emission technique Similarly, twenty-seven healthy human teeth samples from twelve individuals of the age 
group 35-57, were carried out by energy dispersive X-ray fluorescence spectroscopic technique at Institute of Physics, 
Bhubaneswar, India Elements like P, S, CI, K, Ca, Mn, Fe, Cu, Zn, Sr and Pb were quantified in the human bone and teeth 
samples The role and uniformity of the trace elements, present in all the samples, in this study were presented and its effect 
on the statistical distribution of their concentrations is discussed 
Keywords : Human bone, PIXE. EDXRF 
PACS Nos. : 91 65 Nd, 78 70 En 
1. Introduction 
Because most essential trace metals are present in biological specimens in very low 
concentrations, precise and accurate analysis is most essential if meaningful results 
are to be obtained. Mineral and trace elements are not distributed homogeneously in 
human bone and the distribution is not clearly solved. While in the substantia 
compacta (SC) and in the substantia spongiosa (SS) elements seem to be distributed 
nearly equally, concentrations of these elements in the transient zone between SC 
and SS are obviously altered [1]. Understanding the effects of trace metals on human 
health is as complex as it is fascinating. As mentioned earlier, the high concentrations 
may prove toxic, as also, depletion in the concentration of the essential trace 
elements may cause various metabolic instabilities due to enzyme dysfunction. In the 
era of rapid industrialization and technological advances, it is imperative to watch 
keenly for contamination of the environment and its vital composition from heavy metal 
wastes emanating out of industries. Many metabolic disorders in man are accompanied 
'Corresponding Author © 2 0 0 7 l A CS 
100 T R Rautray, Satrujit Mishra, S KPatnaik, V Vijayan and S Panigrahi 
by alterations in the concentration of one or more trace elements in some body fluid, 
especially blood serum or plasma. It is thus important to update us with various 
techniques available for such determinations, their operational aspects, advantages/ 
disadvantages etc. [2]. 
The tooth is a bio-indicator of great interest because it contains information on 
exposure to elements that become deposited in the tooth material. The mineral tissue 
of the tooth consists of hydroxyapatite crystals with incorporated trace elements, 
which can provide information, concerning environmental influence and dietary habits. 
Trace elements may also pay a role in dental health [3], 
2. Experimental techniques 
2.1. Sample preparation : 
The bone samples were collected from the City Hospital, Berhampur, India from an 
individual of age 54 who died of an accident. The samples were collected from 
different parts of the human body by autopsy. To keep contamination and loss of 
elements from the samples to a minimum, instruments were used for the collection 
of specimens and their handling prior to the analysis were acid cleaned and washed 
with Millipore water and then with alcohol. For Particle Induced X-Ray Emission (PIXE) 
analysis, after crushing the samples to fine powder, 150 mg of each of the specimens 
were added with high pure graphite (99.99%) powder in 1 : 1 ratio by mass and the 
mixture had to be ground thoroughly to make a homogeneous mixture. Pellets of size 
13 mm diameter were obtained after putting the mixture in the KBr press [4]. Similarly 
for the Energy Dispersive X-Ray Fluorescence (EDXRF) analysis, 500 mg of the 
specimens were added with high pure cellulose powder in 1 : 1 ratio by mass and 
ground thoroughly to make a homogenous mixture and pressed in the KBr press to 
get pellets of size 25 mm diameter [5]. 
2.2. Data analysis : 
For PIXE analysis, the bone samples were irradiated in vacuum inside the scattering 
chamber at the 3 MV tandem type horizontal pelletron accelerator with a proton beam 
of energy 3 MeV at Institute of Physics, Bhubaneswar, India. The data analysis was 
performed by using GUPIX-2000 software [5]. The EDXRF system at the Institute of 
Physics has been used for the analysis of human teeth samples. The spectra 
obtained for all the samples were evaluated using the AXIL computer program supplied 
by the International Atomic Energy Agency (IAEA). For both PIXE and EDXRF data 
acquisition, Si (Li) detector was used. A 50 /*m aluminized mylar was used for PIXE 
data acquisition for low energy suppression. Target of a certified reference material 
was also prepared for analysis in the EDXRF system as standard [6]. 
3. Results and conclusion 
In the human bone and teeth samples, Clf Ca and P were quantified to be the major 
Analysts of human bone and teeth 101 
elements, whereas other elements like S, K, Mn, Fe, Cu. Zn, Sr and Pb were 
estimated in trace level in the present investigation. Because of their appreciable rate 
of bone renewal human bones can be expected to record lifelong intake of some trace 
elements The PIXE spectrum of human tibia bone is Sjhown in Figure 1 and the 
EDXRF spectrum of a representative human teeth sample is shown in Figure 2 
10 15 
Energy (keV) 
Figure 1. PIXE spectrum of tibia bone 
Energy (keV) 
Figure 2. EDXRF spectrum of a teeth sample 
Calcium and phosphorous . 
Since human bone and teeth contains hydroxyapatite [Ca10(PO4)6(OH)J as their main 
constituent, which contains higher amount of calcium and phosphorous in it, hence 
the higher amount of- Ca and P is obvious in the samples. In the teeth samples, Ca 
and P amount were found to be much higher than the human bone samples. This 
may be due to the fact that the human tooth enamel contains higher concentration 
of hydroxyapatite. In the present study, Ca and P concentrations were estimated to 
be 28.1% and 13.6% respectively for tibia bone. In the parietal bone sample, 
concentrations of Ca and P were 21.9% and 7.2% respectively whereas for occipital 
bone sample, Ca and P concentration were estimated to be 24.9% and 9 2% 
respectively. 
Moreover, the average concentrations of Ca and P for 27 human teeth samples 
were found to be 35.2% and 20.6% respectively. Comparing the concentration of Ca 
and P in the tibia bone to that of parietal and occipital bones, it was found that the 
Ca and P values are higher in tibia bone sample. This higher concentration may be 
due to presence of higher amount of hydroxyapatite in the tibia bone sample. 
Moreover, Ca/P ratio in hydroxyapatite should be 1.67. But, since the Ca/P ratio in 
the present study does not agree with that of the standard Ca/P ratio, it may be 
stated that the excess Ca concentration is due to some other complexes of Ca other 
than hydroxyapatite. 
Calcium versus zinc, strontium and lead : 
The strontium content of bones can also provide information about the diet of past 
102 TRRautray, SatrujitMishra, SKPatnaik, VVijayanandSPanigrahi 
populations [7]. Natural strontium levels in living bone are typically 150-200 ppm. But 
in the present study, the concentration of Sr in the samples is higher than the normal 
level (tibia bone : 258.7 ppm, occipital bone : 190.2 ppm, parietal bone : 218.6 ppm 
and average concentration of teeth : 285.6 ppm). An interesting observation has been 
found that the Ca/Sr ratio is directly proportional among all the human bone and teeth 
samples. However, the surprisingly positive Ca and Sr correlation must be of 
completely different origin because of the general fact that Ca is substituted by Sr 
and therefore a negative correlation between Ca and Sr is expected. The extent to 
which strontium is subject to diagenetic alteration is a matter of debate, though it is 
widely believed to be one of the least affected elements. Analysis of ancient diet 
using, for example, strontium-calcium ratios requires that elemental levels correspond 
to those present at the time of death i.e. that they reflect in vivo conditions. In a 
similar manner Ca/Zn concentration is also directly proportional among all the human 
bones and teeth samples. Zinc (tibia bone : 26.7 ppm, occipital bone : 1.3 ppm, 
parietal bone : 20.2 ppm and average concentration of teeth : 32.2 ppm) and 
strontium are more evenly distributed and are found to correlate quite well with the 
calcium concentration. Zinc plays an important role in the growth of new skeletal 
tissue and is localized in areas of bone formation. Zinc is also involved in the general 
metabolism of humans so that relations may exist between dietary intake, diseases, 
or occupational exposure and the bone mineral composition. 
Since the present investigation is a preliminary study, our future work will 
concentrate on finding the role of every element in order to find conclusions regarding 
diet, physiology and contamination. Since Pb intake occurs via the walls of narrow 
bone channels inside the bone structure as is clearly visible in the PIXE spectra, so 
few ppm of Pb (tibia bone : 66.8 ppm, occipital bone: 36.3 ppm, parietal bone: 37.1 
ppm and average concentration of teeth: 41.9 ppm) is present in the human bone and 
teeth samples. Ca/Pb concentrations are also directly proportional among each of the 
samples except the higher concentration of Pb in the tibia bone. Higher concentration 
of Pb in the tibia bone sample may be due to contamination with environmental lead 
containing materials or during sample preparation. Other elements like S, CI, K, Mn, 
Fe and Cu were also estimated in the present study and are as shown in Figure 1 
and Figure 2. 
References 
(1] P Wobrauschek, G Pepponi, C Streli, C Jokubonis, G Falkenberg and W Osterode, Adv. X-RayAnal. AS 
478 (2002) 
[2] URL: http://vMw.ojhas.org/issue13/2005-1~1.htm 
[3] M L Carvalho. J P Marques, J Brito, C Casaca and A S Cunha Nucl. In strum. Meth. B196 148 (2002) 
[4] M Ashok. S Narayana Kalkura, V J Kennedy, A Markwitz, V Jayanthi, KQM Nair and V Vijayan Int. J. 
PIXE 12 137 (2002) 
[5] V Vijayan, T R Rautray. P K Nayak and D K Basa X-Ray Spectrom. 34 128 (2005) 
[6] V Vijayan, S N Behera, V S Ramamurthy, S Puri, J S Shahi, N Singh X-Ray Spectrom. 26 65 (1997) 
I?1 RJon ^ l ? ThB Anaiysi$ of Preh*toric Diets (eds.) R I Gilbert and J H Mielke (Orlando : Academic) 


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