Electrical and Optical Properties of Hydrogenated

0 downloads 0 Views 710KB Size Report
of this property is an increased efficiency for optical transitions. Thus, the absorption coefficient ..... O ______ ______ ______ ______ . 0.4. 0.5. 0.6. 0.7. 0.8.
ANNUAL REVIEWS

Ann. Rev. Mater. Sci. 1980. 10: 43-63 Copyright © 1980 by Annual Reviews Inc. All ril/hts reserved

Further

Quick links to online content

ELECTRICAL AND OPTICAL

x8643

PROPERTIES OF

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

HYDROGENATED AMORPHOUS SILICON! J. I. Pankove and D. E. Carlson RCA Laboratories, Princeton, New Jersey 08540

INTRODUCTION

Hydrogenated amorphous silicon (a-Si: H) was first made from a glow discharge in silane (SiH4), and the properties were investigated by Chittick et al in 1969 (1). They showed that the dark conductivity depended strongly on substrate temperature varying from .:$10- 10 (O-cm)-1 for depositions near room temperature to 10-5 (O.cm)-1 for depositions at 550°C. They also observed a large photoconductive effect for films deposited at temperatures between 200 and 400°C. In 1972, Spear & LeComber (2) used a field effect technique to show that the density of gap states in a-Si: H was significantly lower than in evaporated amorphous silicon. In 1975, these same authors (3) published a detailed study of the substitutional doping of a-Si: H by adding either PH3 or B2H6 to the SiH4 discharge. The first papers discussing a-Si: H p-n junctions (4) and photovoltaic devices (5) were published the follow­ ing year. In the last few years, several investigators (6-9) have fabricated a-Si: H solar cells with conversion efficiencies in the range of 4-6 %. The purpose of this paper is to review recent developments involving the optical, electrical, and photovoltaic properties of a-Si: H. '"

'"

'"

'"

OPTICAL ABSORPTION IN a-Si: H Effect of Amorphous Structure on Absorption

In an amorphous material, crystal momentum is not a good quantum number. Therefore, optical transitions may be thought of as localized 1 Research reported herein was prepared for the Department of Energy, Division of Solar Technology, under Contract No. EY-76-C-03-1286 and RCA Laboratories, Princeton, New Jersey 08540.

43 0084-6600/80/0801-0043$Ql.00

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

44

PANKOVE & CARLSON

transitions (where momentum is usually readily conserved). A consequence of this property is an increased efficiency for optical transitions. Thus, the absorption coefficient for a-Si: H is one order of magnitude larger than that of crystalline silicon, c-Si, in the visible portion of the spectrum (Figure 1) (10, 1 1). The high absorption coefficient of a-Si: H makes this material particularly suitable for photovoltaic applications: 1 }lm of a-Si: H is sufficient to absorb most of the usable solar radiation, compared to 100 J-lm for c-Si. The advantage of the small amount of material required coupled to the unconcern for crystallinity may eventually result in low-cost solar cells (5). Role of Hydrogen

Because of their inherent disorder, amorphous materials could have a large concentration of dangling bonds. The dangling bonds produce states inside the energy gap that can act as carrier traps (reducing the mobility) or as nonradiative recombination centers that decrease the carrier lifetime. These two effects are highly undesirable in most devices. However, in a-Si: H, hydrogen passivates the dangling bonds, thus eliminating many traps and nonradiative recombination centers. Another consequence of the high concentration of hydrogen is that the energy gap of amorphous Si is much larger than that of crystalline Si: typically 1.7 ±0.2 eV for a Si : H compared to 1. 1 eV for c-Si ( 1 1). This is because the Si-H bond has a higher binding energy than the Si-Si bond, so that the average binding energy of the hydrogenated material is larger than that of pure Si. Furthermore, since the energy gap scales with the binding energy ( 12), a larger energy gap is obtained in a-Si: H. Since hydrogen ties dangling bonds, the corresponding states are removed from the energy gap. The reduced density of states inside the gap renders doping more effective in controlling the position of the Fermi level. Hence, it is possible to make a-Si: H n-type or p-type at will (a control not achievable in nonhydrogenated amorphous Sil -

o

ELECTRICAL PROPERTIES Electrons and holes in undoped or lightly-doped a-Si: H are transported mainly via the extended states at room temperature ( 13). At high doping levels, impurity-band conduction appears to become the dominant transport mechanism, i.e. hopping conduction occurs within bands formed by the dopants ( 13). However, there is some experimental

HYDROGENATED AMORPHOUS SILICON

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

10

6

45

r-----�----�--,_--r_--,

0-

SIL. i

...

_ __ __

1/ //

I

I

o

T 2 o tI

_SINGLE CRYSTAL Si

4 10

,

LOVELAND ET AL.

/

I I I

I I I

.8

.7

Figure 1

.6

X(jLm)

.5

.4

Absorption spectra of a-Si: Hand c-Si.

.3

46

PANKOVE & CARLSON

evidence that hole conduction in p-type material is limited by the formation of small polarons (14) or self-trapped holes (15). An analysis of high-field conduction in forward-biased Schottky diodes indicates that the Poole-Frenkel mechanism operates in most cases (c. R. Wronski, D. E. Carlson, unpublished results). The Pooie-Frenkel expression is given by

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

1

where 0"0, BpF, and k are constants, E is the electric field, and T is the temperature (16). Figure 2 shows some high-field conduction data for films 0.15 Jim and 1.2 Jim thick. Both films obey Equation 1 for fields greater than ",4 x 104 V/cm. Moreover, the dielectric constant (K) as determined from the high-field slope in Figure 2 is '" 10 (close to the expected value of '" 12). This field ionization of carriers out of traps may be partially responsible for the high collection efficiency of carriers photogenerated in the space-charge region of a-Si: H solar cells. In some devices, the high-field transport can be more accurately described by space-charge-Iimited conduction (9); the density and dis-

-4 r------r---,Ir---.--.---�--_, 10

0.15f.Lm Dd=1.2fLm o d

-

I

--

E

=

{3 PF=3.78xI0 K

=

10

24

mks

-5 10

I

c::

b

-6 10 1000 Figure 2

Conductivity as a function of the square root of the electric field.

HYDROGENATED AMORPHOUS SILICON

47

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

tribution of defects depend strongly on deposition conditions, and thus different conduction mechanisms might be expected to dominate in samples made under different conditions. Conduction measurements of a-Si: H films in planar geometries are complicated by light-induced (17, 18) or adsorbant-induced effects (19). It is clear that some of these effects are due to band bending near surfaces or interfaces (18, 19), but bulk effects may also be occurring in some cases (17).

DEVICE STRUCTURES Several types of a-Si: H electronic structures, such as Schottky barriers, p-n junctions, and p-i-n junctions, have been employed to investigate the electrical and photovoltaic properties of the material (4-6). The Schottky-barrier devices are usually fabricated by depositing a thin ( 10-50 nm) phosphorus-doped layer of n + a-Si: H on a metal substrate (e.g. steel) followed by an undoped layer 0 3 1 0 flm thick. The barrier is then formed by evaporating a high work-function metal such as Pt onto the undoped (but slightly n-type) a-Si: H (6). A p-i-n device can be fabricated by depositing a thin ( 10-20 nm) boron-doped layer of p­ type a-Si: H on top of the undoped layer, and then depositing a top contact such as Pt. P-i-n devices have also been fabricated on glass sub­ strates coated with indium-tin-oxide (5) in which case the p-Iayer is deposited first. �



.

-

.

'"

PHOTOVOLTAIC PROPERTIES Minority Carrier Transport

The minority carrier transport is critical in photovoltaic devices. The photogenerated minority carrier must have either a diffusion length or drift length (in a built-in field region) of the order of eX- \ where a is the absorption coefficient of the absorbed light. Recent measurements on back-illuminated, Schottky-barrier cells indicated that the hole diffusion length is < 40 nm in undoped a-Si: H (20). Since drift mobility measure­ ments indicate an extended-state mobility (flh) of the order of 1 cm2/V-s for holes (21), the lifetime ('h) is only of the order of 1 ns. Efficient collection of carriers occurs only for those carriers that are photogenerated in the space-charge region of a-Si: H solar cells (22). However, since the hole lifetime is of the order of 1 ns, recombination can occur even in the space-charge region where the drift length (flh ThE) is on the order of 0.1 flm for a field of 104 V/cm. In devices exhibiting large short-circuit current densities (J sc :­ lV, .7 z w I­ z

�.6

� w � w.5 � � :::>



g!4 o J: Cl.

.3

.2

.1

1.6

IA

-

hlf(eV) 1.2

1.0

0�--------� �------� �---------�---------�----­ 20 3O 4O IO

REVERSE BIAS (V)

Figure 8 Quenching of photoluminescence as a function of reverse bias across the Schottky barrier in a-Si. One inset shows the structure of the diode; the other inset shows the PL emission spectrum of a-Si: H at 78 K.

56

PANKOVE & CARLSON

3.0

t-;.

0

+

+

0

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

+ + + t

2.0

+

0

0

0

0 0

0

0 0 v

+0 0 + 0 +

+

• c...> Q.. c.!) c:::> -I

0 0 0 0

0 n

-I 0....

0

c.!) c:::> -I

+ +

t +

0

+

0 0

1.0

+ +

+ + +

T

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

t0E-3 / T Figure 9

Temperature dependence of photoluminescence and photoconductivity in the

same sample of a-Si: H.

HYDROGENATED AMORPHOUS SILICON

57

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

Temperature Dependence

As a function of temperature, the photoluminescence efficiency remains high up to about 100 K, and then drops rapidly above 150 K with an activation energy of 0. 13 ±0.02 eV for the competing nonradiative process (33, 34, 36). Doping, on the other hand, causes a large drop in efficiency at low temperature, although the temperature dependence is not as pronounced as in undoped a-Si: H, so that at room temperature the luminescence efficiency of the doped material is higher than that of the undoped material (34). The thermal quenching of luminescence may be due not so much to the onset of a competing nonradiative recombination process as to the escape of one or both excess carriers from the radiative recombination center. This concept is supported by the simultaneous measurement of photoluminescence and photoconductivity as a function of temperature (37; also J. I. Pankove, unpublished results). At low temperatures, carrier freeze-out prevents the measurement of transport. However, above 150 K, as the luminescence intensity decreases, the photocurrent increases, and both processes vary with similar activation energies (Figure 9). Since the lifetime of majority carriers at room temperature is of the order of microseconds while the radiative time is less than 20 nsec, it is evident that the luminescence efficiency does not decrease because of shorter carrier lifetime. The only alternative is that the radiative recombination centers are depleted of carriers. '"

Dependence on Hydrogen Concentration The high concentration of hydrogen in a-Si: H (in the range of 5 to 50 atomic %) is known from many different experiments: intensity of infra­ red (IR) vibrational modes (38), hydrogen evolution (24, 39, 40), nuclear reaction (41, 42), secondary ion mass spectrometry (25, 42), electron microprobe analysis (41). The IR absorption spectrum is particularly useful in determining the various types of bonding configurations (-Si-H, =Si=Hz, -Si-H3) because each configuration has a characteristic set of vibrational modes (26, 38). These are listed in Table 1 (38). In one particular study (40), thermal annealing and simultaneous monitoring of the evolved hydrogen was used to gradually dehydrogenate a-Si: H. Then the photoluminescence was studied as a function of de­ hydrogenation. A typical result (Figure 10) shows that dehydrogenation begins at about 350°C and that as the hydrogen concentration in the sample decreases, the photoluminescence intensity decreases also. How luminescence behaves with annealing temperature below 350°C depends

PANKOVE & CARLSON

58

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

Table 1

Infrared vibrational nodes (in cm - 1),

Bonding configuration

Bond stretching

Bond bending or cisor

Bond wagging or rocking

=Si-H =Si=H2 -Si=H3 (SiH2)" b

2000 2090 2120 2090

890 890,850 845, 890

640 640,590 640 630

• From Reference 38. b From Reference 26.

15

en � z ::::>

w >0 -w t-> D:::w ..J

I

o

/ o

200

To

/

/

;60 400

600

( °c )

Figure 10 Luminescence intensity, L, and hydrogen evolved [H] from a-Si: H after a 30-min anneal at indicated temperatures.

59

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

HYDROGENATED AMORPHOUS SILICON

on how the sample was initially prepared. But above '" 350°C, all the a-Si: H samples begin to lose hydrogen and the photoluminescence efficiency decreases. Simultaneously with the loss of hydrogen, one observes a shift of the luminescence spectrum to lower photon energies (Figure 11). The correlation between hydrogen concentration and photolumines­ cence suggests that hydrogen may be involved in the radiative recom­ bination center. Similar luminescence spectra are found in amorphous Si made by sputtering in the presence of hydrogen (43), by low tempera­ ture pyrolysis of silane (44), by evaporation followed by hydrogenation (45), and by amorphization of a single crystal followed by hydrogenation (46,47). Without hydrogen, this luminescence is not observed. However, as the hydrogen escapes, it leaves behind dangling bonds that form centers for nonradiative recombination. Therefore the drop in lumines­ cence efficiency may be dominated by competing nonradiative processes rather than by the decrease in the number of radiative centers. However, both effects may occur simultaneously. It is interesting to note that with �----� 1.3�----�,----��----��--�---I I I • X



x x • x • 6. 0

i



II

II

I.Ir

>

0

-

x 0

-

!x

Q)

205 300 350 450



o

0.9 -

x

II

0.8� o

• •

Ts

100

II

0

-

L-____L-____L-____L-__��__�

____

200

300

To

400

500

600

(OC)

11 Variation of the peak emission energy on annealing temperature for several specimens.

Figure

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

60

PANKOVE & CARLSON

dehydrogenation, the electron spin resonance signal increases, which is consistent with the increased number of dangling bonds (Figure 3) (24). After dehydrogenation, the amorphous Si has a high density of dangling bonds that are very reactive. When an a-Si sample is exposed to atomic hydrogen at a temperature lower than 350°C, the dangling bonds become rehydrogenated (48). This chemical change can be verified by a decreased spin resonance (49), increased photoluminescence (50), and hydrogen evolution upon subsequent heating (48, 50). The recovery of photoluminescence has been followed over four cycles of dehydro­ genation and rehydrogenation in several samples. The ability to hydrogenate dangling bonds has been extended to single crystals of Si where the surface is covered with dangling bonds that are responsible for the leakage current of reverse-biased diodes. After hydro­ genating the surface of an exposed p-n junction, one observes a dramatic drop in leakage current (48). Models for the Luminescent Transition in a-Si: H

In spite of the numerous experiments performed on a great variety of samples, there is still no definitive consensus about the nature of the

luminescent transition. Among models proposed are tail-to-tail-state transitions (35, 51), donor-to-acceptor transitions (34, 52), bound exciton recombination (37), and recombination with a polaron or with a self­ trapped hole (15). Support for the polaron or the self-trapped hole models comes from the observation of a large Stokes shift (15), of the order of 0.5 eV (the energy gap being � 1.8 eV and the luminescence occurring at � 1.3 eV). When a correction is made for the photoluminescence efficiency to express it per absorbed photon, the efficiency seems to remain constant through­ out the measurable range below � 2.1 eV (34). However, since the ab­ sorption constant below the energy gap is low, it can be detected only by internal photon-counting techniques such as photovoltaic or photo­ conductive measurements. No photoluminescence data is available for lower-than-band-gap excitation, except for excitation by 1.06-llm laser light that may result in a two-photon transition. The bound exciton model was derived from the field dependence of photoluminescence suggesting that an applied electric field could disso­ ciate the geminate pairing of a bound exciton (37). However, an electric field can also separate electrons and holes that are not paired and thus reduce their recombination efficiency. The models of tail-to-tail-state and donor-to-acceptor transitions readily come to mind when one considers the time-resolved spectra, which show a large spread of time constants for the luminescence decay

61

HYDROGENATED AMORPHOUS SILICON

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

(18 usec to 10 msec) (see Figure 12) (15,35,53). A long decay time is best explained by a tunnelling-assisted radiative recombination between electrons and holes localized at spatially separated sites. Note that the fact that such long recombination times can be found indicates that non­ radiative recombination is negligible. The main support for tail-to-tail-state transitions is the observation by Tsang & Street (15) of a large spectral shift to lower energy with time (red shift by 0.15 eV). However, such a large red shift has not been observed by other researchers using different samples (34, 35).

en -

§

.0 �

10

4

o -

>-

t

o Z

; • • •

...

(/) 10 Z W tZ W

�•

Searle et ai,ref. 53 (sputtered, 1.25 eV )

3

102

w

Searle e t ai,ref. 53

'1 .... ... .. ./ (GO, undoped, 1.19 eV) ':Y... . 11 '" .oQ� 0 �.. 0 /' /' I "'---� 00 s:'-...! Kurita et 01 ref 35�.., 0 (GO,undoped,1.2geV ) .... 0 0 � • .... '-

'. N :o� "-





....

.

..

o

ffi z �

:::> .J

10

Tsang

+





0

• • •

Street ref. 15

( GD,undoped,1.3eV)



.

A

A



0 -.. '\ ·.0 ·.0 0 .0 0











��------�--L---�·O 0.01 0. 1 I 10 100 • •

TIME

(fLS)

Figure 12 Luminescence decay at liquid-nitrogen temperature for samples of different origin. The curves are shifted with respect to intensity by about equal amounts. In Ref. 53, an excitation energy of 2.34 eV with pulse width of 7 ps was used; in Ref. 15,2.40 eV and 20 ns; in Ref. 35,3.67 eV and 4 ns. The authors are grateful to W. Czaj a for making this figure available in advance of pUblication.

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

62

PANKOVE & CARLSON

The donor-to-acceptor transition is suggested by the absence of a spectral shift when the excitation intensity is varied. This result indicates that the radiative recombination occurs between two fixed distributions of states regardless of how high above the donors and how far below the acceptors intrinsic states are occupied by electrons and holes, respectively. Further support for this model comes from recent observa­ tions in some samples of a peak in the photovoltaic and photoconductive spectra at � 1.2 eV attributed to optical transitions from acceptors to donors (54). A band of donors 0.45 eV below the conduction band has been found by Balberg using tunnelling spectroscopy (55). This measurement also indicates transport within the impurity band. Although there is no evidence for an acceptor band, acceptors may still be present, too far apart to allow hopping transport, but participating in the luminescence process.

CONCLUSION Hydrogenated amorphous silicon is endowed with efficient optical transitions, and a reduced density of gap states due to the passivation of dangling bonds by hydrogen. Moreover, minority carrier transport has been shown to occur over distances of � 0.5 /lm. Hence, hydrogenated amorphous silicon is a new type of photovoltaic material that may lead to low-cost terrestrial solar arrays within the next few years. Literature Cited

1. Chittick, R. c., Alexander, J. R., Sterling, R. f. 1969. J. Electrochem. Soc. 116: 7781 2. Spear, W. E., LeComber, P. G. 1972. J. Non-Cryst. Solids 11: 219-34 3. Spear, W. E., LeComber, P. G. 1975. Solid State Commun. 17; 1193-96 4. Spear, W. E., LeComber, P. G., Kinmond, S., Brodsky, M. 1976. Appl. Phys. Lett. 28: 105-7 5. Carlson, D. E., Wronski, C. R. 1976. Appl. Phys. Lett. 28 :671-73 6. Carlson, D. E. 1977. IEEE Trans. Electron Devices ED-24: 449-53

7. Wilson, 1. I. B., McGi ll, 1., Kinmond, S. 1978. Nature. 272: 153 8. Hamakawa, Y, Okamoto, H., Nitto, Y. 1979. Appl. Phys. Lett. 35:187-89 9. Gibson, R. A., Spear, W. E., LeComber, P. G., Snell, A. 1. 1979. Proc. 8th Int.

Can;: on Amorphous and Liquid Semi­ conductors. Cambridge. Mass. To be

published

10. Loveland,R.J.,Spear,W. E.,AI-Sharbaty, A. 1973/74. J. Non-Cryst. Solids 13: 5568 11. Zanzucchi, P. J., Wronski, C. R., Carlson, D. E. 1977. J. Appl. Phys. 48: 5227-36 12. Joannopoulos,1. D., Cohen, M. L. 1976. Solid State Phys. 31: 71-148 13. Spear, W. E. 1977. Adv. Phys. 26: 811-45 14. Beyer, W., Mell, R. 1977. Proc. 7th Int.

15. 16. 17.

18.

Can! on Amorphous and Liquid Semi­ conductors, Edinburgh, ed. W. E. Spear, p. 333. CICL, Univ. Edinburgh Tsang, c., Street, R. A. 1979. Phys. Rev. B 19: 3027-40 Simmons, 1. R. 1967. Phys. Rev. 155:

657-60

Staebler, D. L., Wronski, C. R. App/. Phys. Lett. 31; 292-94 Solomon, 1, D iet l, T., Kaplan, D. 1. Phys. Paris 39: 1241-46

1977.

1978.

19. Tanielian, M., fritzsche, R., Tsai, C. c., Symbalisty, E. 1978. App/. Phys. Lett. 33: 353-56

HYDROGENATED AMORPHOUS SILICON 20. Staebler, D. L. 1979. See Ref. 9 21. Allan, D. 1978. Phi/os. Mag. 38:381-92 22. Wronski, C. R. 1977. IEEE Trans. Electron Devices ED- 24: 351-57 23. Hanak, 1. J., Zanzucchi, P. J., Carlson, D. E., Wronski, C. R., Pankove, 1. I. 1977. Proc. 7th Int. Vacuum Congr. and 3rd Int. Con! Solid Surfaces,

24.

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

25. 26. 27. 28. 29. 30. 31. 32. 33.

Vienna,

ed. R. Dobrozinsky, F. Rudenauer, F. P. Viehbock, A. Breph, pp. 1947-49. Horn, Austria: Burger Fritzsche, H., Tsai, C. c., Persans, P. 1978. Solid State Technol. 21 : 55-60 Carlson, D. E., Magee, C. W. 1978. Appl. Phys. Leu. 33: 81-83 Knights, 1. c., Lucovsky, G., Nemanich, R. J. 1979. J. Non-Cryst. Solids 32: 393403 von Roedern, B., Ley, L., Cardona, M. 1977. Phys. Rev. Lett. 39: 1576-80 Carlson, D. E., Magee, C. W., Triano, A. R. 1979. J. Electrochem. Soc. 126: 688-91 Carlson, D. E. 1977. Tech. Dig. 1977 IEEE Int. Electron Devices Meet. pp. 214-17 Carlson, D. E. 1979. See Ref. 9 Williams, R. 1979. J. Appl. Phys. 50: 2848-52 Ovshinsky, L. R., Madan, A. 1978. Nature. 276: 482-84 Engemann, D., Fischer, R. 1974. Proc. 12th Int. Conj. on Physics of Semi­ conductors, ed. M. H. Pilkuhn, pp. 1042-

46. Stuttgart: Teubner 34. Nashashibi, T. S., Austin, 1 G., Searle, T. M. 1977. Phi/os. Mag. 35: 831-35 35. Kurita, S., Czaja, W., Kinmond, S. 1979. Solid State Commun. 32: 879-83 36. Pankove, 1. I., Carlson, D. E. 1976. Appl. Phys. Lett. 29: 620-22 37. Engemann, 0., Fischer, R. 1976. AlP Can! Proc. 31:37-43 38. Brodsky, M. H., Cardona, M., Cuomo,

63

J. J. 1977. Phys. Rev. B 16:3556-71 39. Triska, A., Dennison, D., Fritzsche, H. 1975. Bull. Am. Phys. Soc. 20: 392 40. Pankove, 1. 1, Carlson, D. E. 1977. Appl. Phys. Lett. 31: 450-51 41. Brodsky, M. H., Frisch, M. A., Ziegler, J. F., Lanford, W. A. 1977. Appl. Phys. Lett. 30: 561-63 42. Clark, G. 1., White, C. W., Allred, D. D., Appleton, B., Magee, C. W., Carlson, D. E. 1977. Appl. Phys. Lett. 31: 582-85 43. Paul, W., Lewis, A. J., Connell, G. A. N., Moustakas, T. D. 1976. Solid State Commun. 20:969-72 44. Hirose, M., Taniguchi, M., Osaka, Y. 1977. See Ref. 14, pp. 352-56 45. Kaplan, D., Thomas, P. A., Sol, N., Velasco, G. 1978. Appl. Phys. Lett. 33: 440-42 46. Peercy, P. S., Stein, H. J. In preparation 47. Pankove, 1. 1, Wu, C. P. 1979. Appl. Phys. Lett. 35: 937-39 48. Pankove, J. I., Lampert, M. A., Tarng, M. L. 1978. Appl. Phys. Lett. 32: 439-40 49. LeComber, P. G., Loveland, R. 1., Spear, W. E., Vaughan, R. A. 1973. Proc. Fifth Int. Con! on Amorphous and Liquid Semiconductors, Garmisch-Par­ tenkirchen, pp. 245-50. London: Taylor

and Francis (Pub!. 1974) 50. Pankove, 1. I. 1978. Appl. Phys. Lett. 32: 812-13 51. Street, R. A. 1978. Phi/os. Mag. B37: 3542 52. Morigaki, K., Dunstan, D. 1., Cavenett, B. c., Dawson, P., Nicholls, 1. E., Nitta, S., Shinakawa, K. 1978. Solid State C ommun. 26: 981-84 53. Searle, T. M., Nashashibi, T. S., Austin, I. G. 1980. Phi/os. Mag. In press 54. Pankove, J. I., Pollak, F. H., Schnabolk, C. 1979. See Ref. 9 55. Balberg, I. 1979. See Ref. 9

ANNUAL REVIEWS

Further

Quick links to online content Annual Review of Materials Science Volume 10, 1980

CONTENTS PREFATORY CHAPTER

Unity of Concepts in the Structure of Matter, John Bardeen

Annu. Rev. Mater. Sci. 1980.10:43-63. Downloaded from www.annualreviews.org by University of Groningen on 03/14/11. For personal use only.

EXPERIMENTAL AND THEORETICAL METHODS

Small Angle Neutron Scattering of Polymers, Robert Ullman

261

PREPARATION, PROCESSING, AND STRUCTURAL CHANGES

Cold Forming of Polymeric Materials, M. T. Shaw

19

Electrocrystallization, E. Budevski, V. Bostanov, and G. Staikov

85

Preparation of Glassy Metals, H. S. Chen, H. J. Leamy, and C. E. Miller

363

PROPERTIES AND PHENOMENA

The Metal-Semiconductor Interface, J. O. McCaldin and T. C. McGill

65

Energy Levels in Silicon, J.-w. Chen and A. G. Milnes

157

Mechanical Properties of Composites, Tsu- Wei Chou and Anthony Kelly

229

Positron Annihilation Spectroscopy, R. W. Siegel

393

SPECIAL MATERIALS

Electrical and Optical Properties of Hydrogenated Amorphous Silicon, J. 1. Pankove and D. E. Carlson

Superconducting Materials, R. M. Scanlan

43 113

Liquid Crystals, S. Chandrasekhar and N. V. Madhusudana

133

Materials for Heterojunction Devices, H. Kressel

287

High Modulus/High Strength Organic Fibers, W. Bruce Black

311

INDEXES

Author Index

427

Subject Index

440

Cumulative Index of Contributing Authors, Volumes 1-10

453

Cumulative Index of Chapter Titles, Volumes 1-10

455