Study of Beta Radioisotopes Direct Energy Converters

by Y. Ngu and M. Litz

ARL-TR-4969 September 2009

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Army Research Laboratory

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ARL-TR-4969 September 2009

Study of Beta Radioiostopes Direct Energy Converters

Y. Ngu and M. Litz

Sensors and Electron Devices Directorate, ARL

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Study of Beta Radioisotopes Direct Energy Converters

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Y. Ngu and M. Litz

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14. ABSTRACT

Energy stored in the nucleus of radioisotopes contains energy-densities five orders of magnitude higher than the energy-density 

of chemical bonds. The decay modes (and decay products) of these high-energy-density materials can then be matched to direct 

energy conversion materials for best efficiency. The choice of converter material, packaging geometry, thickness of material

layer, and number of layers will necessarily depend on the specific radioisotope output product (alphas, betas, or gammas) and 

the energy of the particles (17 eV up to 5.5 MeV). Samples of silicon (Si) and silicon carbide (SiC) p-i-n diodes have been 

irradiated with betas from 90Sr and 63Ni. The voltage and current of the devices prior to irradiation were measured and 

compared to measurements made during periods of radiation. The sample diodes generate on the order of 10 pW in the 

presence of a 7.5 mCi source. This represents a direct-energy-conversion of beta-radiation to electrical power efficiency of

~7%.

15. SUBJECT TERMS

Direct energy conversion, isotope battery, beta-battery 

16. SECURITY CLASSIFICATION OF: 

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 ABSTRACT

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M. Litz

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iii

Contents

List of Figures iv

List of Tables iv

1. Background 1

2. Devices 3

3. Measurement Setup 5

4. Results and Discussion 7

5. Conclusions 12

6. References 14

List of Symbols, Abbreviations, and Acronyms 15

Distribution List 16
iv

List of Figures

Figure 1. A 100 mW sensor uses one AAA battery per day. This energy demand creates 

large logistics requirements that are difficult to support. ..........................................................2

Figure 2. Energy stored in several commercial and military style batteries in common use. ........3

Figure 3. (Left) Diode layout and contact for diode# 1–14 (left) and diode# Q1–Q7 (right)........4

Figure 4. SiC p-i-n diode pairs: (a) diode layout with three leads (diodes numbered Exx); 

(b) diode layout with two leads (diodes numbered Sxx); (c) top view of the diode pairs; 

and (d) picture of the three-lead diode pair................................................................................5

Figure 5. Current flow under (a) open circuit and (b) load conditions...........................................5

Figure 6. I-V curves of a conventional photovoltaic cell with and without light. .........................6

Figure 7. 63Ni radioisotope sources: (a) single source and (b) source pair.....................................6

Figure 8. Eight stacked diode pairs with 14 sources (7 pairs). .......................................................7

Figure 9. Baseline I-V curve of Qynergy diodes (diodes Q1–Q7).................................................8

Figure 10. Baseline and 63Ni radiation I-V curve: (a) diode S11; (b) diode S21; (c) diode 

E11, and (d) diode E12. .............................................................................................................9

Figure 11. 63Ni radiation I-V curve: (a) diodes S11 and S21 as single diode and in parallel 

(D1-2) and (b) diodes E11, E12, S11, and S21 as single diode and in parallel (P4). ..............10

Figure 12. 63Ni radiation time vs. current with no biasing of stacked structure. The 

background line represents lab noise and the stacked diodes line is the radiation 

measurement. ...........................................................................................................................11

Figure 13. 63Ni radiation, showing unusual radiation data from a properly functioning diode 

(diode S11)...............................................................................................................................12

List of Tables

Table 1. Device description. ............................................................................................................4
1

1. Background

Awareness of power and energy priorities have been elevated in recent years because of the 

realization of the finite resources of oil, made clearer from our increasing rate of consumption. 

The solutions include both conservation and development and use of alternative energy sources. 

The military has much to gain from efficient platforms that reduce logistics burden, relieving the 

duty to protect the energy supply chain and thus saving lives in operational activities. Science 

and technology contributions in the form of ultra-light structural materials and alternative fuel 

auxiliary power capabilities are two areas that can have great impact. Alternative fuels include 

the use of fuel cells and rechargeable battery systems for electronic and Soldier power 

applications. Situational awareness (SA) technologies and unattended sensors that use renewable 

and rechargeable technologies are quickly helping to change the SA capabilities on the 

battlefield as well as in commercial activities. 

Small-sensor technology is mission critical for future operational scenarios and depends on asyet undeveloped micro-power sources. While many sensors are expendable for short-term 

applications, a host of sensors are required for longer-term applications. These sensors include 

environmental monitoring applications, embedded sensors for materials and structural integrity, 

and place-and-forget sensors to monitor personnel movement in caves and tunnels. The power 

levels associated with unattended sensors coincide with those of typical energy harvesting 

applications. Energy conversion and storage technologies are fundamental to the harvesting of 

energy from the local environment. Energy harvesting techniques can have particular impact in 

micro-power applications (1 nW to 100 mW) and Soldier power (1 W to 100 kW) regimes. 

The needs of the Army are not stagnant. At this time, the real-time demands to adapt to the 

environment, increase operational pace, and operate within logistical limitations have never been 

greater. Nuclear batteries can have a small but significant impact as a power sources for longlived sensors (1–3). Consider embedded sensors for bridges and foundations of large buildings. 

These sensors can provide information about the structural integrity (4–6). Unattended sensors 

for temperature measurement in the oceans would need no maintenance during an increased 

operational lifetime. Unique opportunities are waiting for sensors and radio frequency 

identification (RFID) tags that benefit from keep-alive power lasting decades. 

Chemical power sources can store the total energy required, but electrical leakage and 

deterioration of the batteries keeps them from delivering the power over a decade. Nuclear 

batteries offer a unique power-source to fill the niche. Even though the energy-density of 

nuclear isotopes is six orders of magnitude greater than that possible in chemical bonds, the 

stigma associated with nuclear materials will require careful design and thoughtful application. 

Sensors embedded in structures, providing information useful to monitor structural integrity (i.e.,

bridges, helicopter blades), may be just the application to overcome these difficulties. 
2

Eliminating the need to maintain power for small sensors can save lives, especially if the sensors 

are in the middle of the battlefield. It can also be operationally important for sensors to remain 

covert. These hidden sensors must remain powered for long periods to maintain the element of 

surprise. Costly maintenance can be avoided when the sensors are not accessible (i.e., at the 

bottom of tunnels, under water, within walls). The crossover point for deciding on the use of 

small isotope powered batteries versus chemical batteries depends primarily on the system power 

requirements and the length of time required to operate. As an example of a representative sized 

system, several small sensors in the inventory, using AA and AAA batteries, require power 

levels of 90 to 9000 mW. The maintenance rate for these useful sensors unfortunately puts 

Soldiers in harm’s way on a daily basis, making the sensors unusable in many scenarios. 

A sensor requiring 100 mW will drain a single AAA battery in less than one day. The power 

drain is compared to battery capacity in figure 1. If 1 W is required by the sensor/load, then the 

1 kg BA5590 will last less than 1 week. The niche for isotope batteries is in situations where 

sensors with relatively low power consumption can be combined with the large amounts of 

energy stored, permitting operational power sources that minimize maintenance schedules, 

saving lives and maintaining covert operations and the element of surprise. Long-lived sensors 

(>10 years) benefit from isotope-based batteries. 

Figure 1. A 100 mW sensor uses one AAA battery per day. This energy demand creates large 

logistics requirements that are difficult to support.

Time Required to Consume Energy Stored

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1 10 100 1000

Average Power (mW)

Joules

day

week

month

AA

AAA

AAA

AA
3

The energy stored in batteries is insufficient to last for the longer periods of time that are relevant 

to military operations. A 10-mW load will use the energy stored in an AA battery in less than a 

month. A 100-mW load will use the energy stored in a BB3590 in less than 6 months. If 1 W is 

required by the sensor/load, then the 1 kg BB5590 will last less than 1 week. Figure 2 shows the 

energy stored in several commercial and military style batteries in common use.

Energy Stored

100

1,000

10,000

100,000

1,000,000

312 AAA AA D BA 5590 Battery

Energy (J)

Figure 2. Energy stored in several commercial and military style batteries in common use.

We have examined the energy conversion capability of multiple semiconductor-based direct 

energy conversion devices. In this report, we analyze the structure of single diodes as it pertains 

to its conversion efficiency and investigate diode architectures to enhance the overall delivered 

energy by stacking individual devices in parallel. This report is structured as follows: section 2

presents the various devices used and their mode of operation, section 3 presents the 

measurement setup, section 4 offers measurement results and a discussion of our observations, 

and section 5 provides closing remarks.

2. Devices

Semiconductor-based radioisotope power converters use the energy generated by the decay of 

radioisotopes to create a power source. A battery of this type is composed of two main parts: 

(1) a radioisotope source of energy and (2) an energy converter (diode) that changes the radiation 

output of the radioisotope energy source into some form of usable electrical energy.

The devices used for energy conversion were silicon carbide (SiC) p-i-n diodes. These diodes 

differed by the thickness of their i-layer and the size of their active area. The names used to 

describe the cells as well as their i-layer size and die size are tabulated in table 1.
4

Table 1. Device description.

Diode # 1 2 3 13 14 Q1 Q2 Q3 Q4 Q5 Q6 Q7

i-layer (μm) 60 60 80 110 110 50 42 35 30 20 10 5

Die size (cm) 0.5 0.5 0.5 0.5 0.5 1 1 1 1 1 1 1

Diode # S11 S12 S21 S22 E11 E12 E41 E42 E62 E72 E81 E82

i-layer (μm) 60 60 60 60 60 60 60 60 60 60 60 60

Die size (cm) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

The devices from table 1 were electrically accessed via three type of connection. The devices 

having only numeric numbers (i.e., 1, 2, 3 ...) were electrically accessed via leads affixed to the 

metal seed layer of the front (n-layer) and back (p-layer). The diodes were mounted at the center 

of a holder such that the backside of the diode was mounted via conducting epoxy to a 

conducting holder and the front side of the diode had small conducting wires soldered to it and

pulled-out to form a lead, as illustrated in figure 3 (left).

The devices having alpha-numeric number with a single digit (i.e., Q1–Q7) were electrically 

accessed with a test fixture. These devices were dies and were not permanently attached to the 

holder. Contact was made to the front side of the die (n-layer) via a probe-like contact; while, 

the backside (p-layer) of the die sat on a copper line given electrical contact to the backside. 

This setup is shown in figure 3 (right).

Figure 3. (Left) Diode layout and contact for diode# 1–14 (left) and diode# Q1–Q7 (right).

The devices having alpha-numeric number with two digits (i.e., S11–E82) were electrically 

accessed via copper strips affixed with conducting epoxy directly to n-layers and p-layers. All 

these devices were pairs of diodes mounted back-to-back, as shown in figure 4. A copper strip 

was sandwiched between the back-to-back diodes to enable contact to each diode’s n-layer,

referred to as the negative terminal (see figure 4 (a)). For devices with numbers starting with E, 

each p-layer of the diode pair had a copper strip epoxy to it (see figure 4 (a)); whereas, the 

devices with numbers starting with S only had one diode with a copper strip epoxy to it while the 

other p-layer was left bare (see figure 4 (b)). The copper strips affixed to the n-layers are 

referred to as the positive leads. There was a 3-mm hole in the copper strip at the center 

of the diode to enable our radioisotope source to be in close contact to the p-layers 

(see figure 4 (c) and (d)).
5

 (a) (b)

(c) (d)

Figure 4. SiC p-i-n diode pairs: (a) diode layout with three leads (diodes numbered Exx); (b) diode layout with two 

leads (diodes numbered Sxx); (c) top view of the diode pairs; and (d) picture of the three-lead diode pair.

3. Measurement Setup

The energetic particles emitted during the decay of the radioisotopes create a multitude of 

electron-hole pairs within the semiconductor (7). Once the carriers are generated, positive 

charges flow into the semiconductor and lead to a generated current Ig, which is equivalent to a 

short circuit current (Isc). The displaced carriers effectively forward bias the p-layer, as seen in 

figure 5 (a), hence creating a voltage potential across the device. The forward bias junction 

yields a current (Id) through the junction that is opposite to the generated current. In the 

presence of very small load (short), Isc = Id, while the output voltage with very high load (open) 

is Voc, the open circuit voltage. When a load is connected to the diode’s output terminals, as in 

figure 4 (b), the current due to the forward bias junction is split between the current into load 

(Iout) and Id such that Ig = Id + Iout.

 

Figure 5. Current flow under (a) open circuit and (b) load conditions.
6

In order to characterize the conversion effectiveness of our diodes, the current through the diode,

as well as the potential across it, needed to be monitored. The conventional approach is to 

perform current versus voltage (I-V) plots, where the voltage across the diodes is swept and the 

current across the diode is recorded. This procedure is then done with no radioisotope (“dark” or 

“baseline” measurement) and in presence of the radioisotope (“radiation”). In the presence of 

radiation, the potential at zero current flow corresponds to open circuit voltage (Voc) while the 

current at zero potential corresponds to short circuit current (Isc). It is expected that the baseline 

and radiation I-V curve would follow the same trend as a photovoltaic cell. The I-V curve of a 

conventional photovoltaic cell is shown in figure 6.

Figure 6. I-V curves of a conventional photovoltaic cell 

with and without light.

Electrical measurements of the diode I-V curve were done with parameter analyzers (HP5155C

and HP5145). The samples were radiated with 90Sr and 63Ni. The 90Sr radiation measurements 

were conducted at the Naval Surface Weapons Center-Carderock (NSWC), MD, using a J. L. 

Shepherd 10 mCi 90Sr cabinet. The 63Ni measurements were conducted with a small (2 mm 

diameter and 50 μm thick) individual coating source sputtered on a thin metal layer. These 

sources can be paired, as illustrated in figure 7, such that their metal layers are in contact, which

enables the diodes to be stacked. Prior to radiation, baseline I-V curves were recorded then a 

radiation I-V curve was recorded during radiation. The I-V curve was conducted between –2 V 

and 2 V by 10 mV increments and long integration (each data point corresponds to the average 

of 16 samples). The parameter analyzer was connected to the diodes via alligator clips.

Isotope source

Metal layer

 (a) (b)

Figure 7. 63Ni radioisotope sources: (a) single source and (b) source pair.
7

In order to increase the overall output current of our direct-energy-conversion (DEC) cell we laid

out diodes in parallel. The parallel structure is assembled by stacking the diodes in separated 

63Ni source pairs. In this arrangement, the copper leads to the p-layers were all connected 

together with copper tapes to make a single positive leads. The same was done with the leads to 

the n-layers to make the negative lead of the stacked structure. A schematic of the stacked cell is 

shown in figure 8. 

63Ni source pair

Positive terminal

(copper tape) Negative terminal

(copper tape)

The isotope sample 

has 2mm diameter 

and is 50um thick 

and fitted into the 

copper foil holes

Figure 8. Eight stacked diode pairs with 14 sources (7 pairs).

4. Results and Discussion

Before performing any radiation measurements, a baseline measurement was conducted for all 

diodes. The baseline measurement is, in effect, a way to test that the cell has proper diode 

behavior. The baseline measurement for the Qynergy diodes is shown in figure 9. In the plot, it 

can be seen that the diodes Q3, Q4, and Q7 do not operate normally—the turn-on point of the 

diodes is at zero potential. No further radiation evaluations were conducted on the diodes that 

were deemed dysfunctional (i.e., Q3, Q4, and Q7). The same measurements were conducted on 

the rest of the diodes and diodes 2, E31, E32, E61, and E71 were also excluded. 
8

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

x 10-8 Diode Baelines 

1

2

3

4

5

6

7

Figure 9. Baseline I-V curve of Qynergy diodes (diodes Q1–Q7).

Once the diodes were screened for proper operation, the radiation measurement was conducted 

by applying the radiation and recording the I-V curve. Figure 10 shows I-V curves from 

0 to 1.2 V for various diodes. The radiation curves are lower than their baseline counterparts, as 

expected. The baseline current at zero potential represents the diodes leakage current; hence, the 

generated current is the difference between the baseline current and the radiation current at zero 

potential. As seen in figure 10 (c), the generated current was found to be as high as 30 pA or as 

low as 2 pA in the case of figure 10 (a) and (b).
9

0 0.2 0.4 0.6 0.8 1

-10

-8

-6

-4

-2

0

2

4

x 10-12

Volts

Amps

S1BAS1.TXT

S1RAD1.TXT

(a)

0 0.2 0.4 0.6 0.8 1 1.2

-1

-0.5

0

0.5

1

1.5

2

x 10-11

Volts

Amps

S2BAS1.TXT

S2RAD1.TXT

(b)

0.2 0.4 0.6 0.8 1 1.2

-6

-4

-2

0

2

4

x 10-11

Volts

Amps

E11BAS1.TXT

E11RAD1.TXT

(c)

0 0.2 0.4 0.6 0.8 1 1.2

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

x 10-11

Volts

Amps

E12BAS1.TXT

E12RAD1.TXT

(d)

Figure 10. Baseline and 63Ni radiation I-V curve: (a) diode S11; (b) diode S21; (c) diode E11, and (d) diode E12.

The generated current from a single diode was determined to be quite low (sometime as low as 

2 pA), so we decided to increase the effective generated current by placing the cells in parallel. 

We tried placing two then four diodes in parallel. Figure 11 presents the I-V curves obtained 

from radiation measurement of the diodes in parallel. In figure 11 (a), D1 and D2 refer to the 

diode S11 and S21, respectively, while D1–2 refers to the parallel combination of the two diodes 

(S11 and S21). The generated current is effectively equivalent to the sum of the individual 

radiation currents of each diode; however, this was not the case once four diodes were placed in

parallel, as can be observed in figure 11 (b), referred to as P4. In both cases, the I-V curve of the 

parallel structure was not the sum of the individual diodes over the entire curve. This behavior is 

potentially due to internal mismatches between diodes. The leakage current and turn-on voltage 

of each diode was different and this could lead to one diode acting as a load on another. When 
10

the diode is off (current is negative), the current from one diode flows through another diode 

instead of the external loop through the parameter analyzer; hence, the recorded parallel current 

is less than the sum of each diode. 

0 0.2 0.4 0.6 0.8 1 1.2

-4

-2

0

2

4

6

8

x 10-11

Volts

Amps

D1RAD1.TXT

D2RAD1.TXT

D1-2RAD1.TXT

(a)

0 0.2 0.4 0.6 0.8 1 1.2

-6

-5

-4

-3

-2

-1

0

1

2

3

4

x 10-11

Volts

Amps

E11RAD1.TXT

E12RAD1.TXT

S1RAD1.TXT

S2RAD1.TXT

P4RAD1.TXT

(b)

Figure 11. 63Ni radiation I-V curve: (a) diodes S11 and S21 as single diode and in parallel (D1-2) and (b) diodes

E11, E12, S11, and S21 as single diode and in parallel (P4).

To maximize the current output, we put eight diode pairs in parallel. This setup used 14 active 

diodes and 63Ni sources. Since the output current obtained from the other parallel combinations 

(two and four diodes) did not yield a linear increase in current over the entire I-V curve, we 

decided to look at the generated current out of this stacked structure over time at zero bias. We 

grounded the n-layer leads and applied 0 V at the p-layer leads and recorded the current through 

the diodes over a 40-s period. The generated current from the eight stacked diode pairs is shown 

in figure 12. The background current identifies the current recorded in the lab with no 63Ni 

source. The stacked diodes generated approximately 2 pA. The generated current was quite 

similar to that obtained from the previously recorded single diode measurements (see figure 10). 

Again, this might be due to the diodes loading each other as well as to an odd behavior observed 

in some of the I-V curves. 
11

5 10 15 20 25 30 35

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

x 10-12 IT Curve 

Background

Stacked diodes

Time (sec)

Current (A)

5 10 15 20 25 30 35

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

x 10-12 IT Curve 

Background

Stacked diodes

Time (sec)

Current (A)

Figure 12. 63Ni radiation time vs. current with no biasing of stacked structure. The background line represents lab 

noise and the stacked diodes line is the radiation measurement.

The I-V curves of some of our diodes followed the unexpected example trained shown in figure 

13, where the radiation generated I-V curve is higher than the baseline curve. This behavior 

could be explained by the idea that the generated current might be flowing in the opposite 

direction to what is commonly expected. Another explanation could be that we could have been

measuring very close to the sensitivity level of the tool (we were in the pico range). The I-V 

curve recorded in figures 10 (a) and 13 were conducted on the same diode on two separate days.

Each behavior was observed more than once and in this and other diodes.
12

0 0.2 0.4 0.6 0.8 1

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

x 10-12

Volts

Amps

S1BAS1.TXT

S1RAD1.TXT

Figure 13. 63Ni radiation, showing unusual radiation data from a properly 

functioning diode (diode S11).

5. Conclusions

Semiconductor-based radioisotope power converters use the energy generated by the decay of 

radioisotopes to directly create a current/power source. Thermal energy conversion is used for 

reactors, but that is not practical for compact packaging. In this report, we have characterized 

SiC p-i-n diodes for energy conversion efficiency. Power output was measured using an I-V 

curve tracer. These diodes differed by the thickness of their i-layer and the size of their active 

area. In order to characterize the conversion effectiveness of our diodes, the current through the 

diodes was monitored by performing I-V plots while sweeping the voltage across the diodes. 

The generated current varied as high as 30 pA and as low as 2 pA for a single diode. Stacking 

the diodes in parallel did not lead to a linear increase in generated current when using up to 14 

diodes. Three stacking approaches (2, 4, and 14 diodes in parallel) were compared. This result 

was most likely due to a diode mismatch in the structure, which decreased with the number of 

diodes in the stack. 

The overall small current and voltage obtained in our preliminary work was due to the large size 

of the depletion region of the diode used (~100 to 500 μm). The efficiency of the diodes can be 

improved by optimizing the diodes (p-i-n layer thicknesses) for our specific application and 

choice of isotope (7). In the future, designs for devices will permit increased generated current 

and open circuit voltage by matching the i-layer thickness with the energy of the electron emitted 

from the isotope decay. Depending on the isotope used and the length of time to be operated, 

SiC p-i-n diodes could be substituted in place of Si p-i-n diodes for longer operation, because 

SiC is more resistant to radiation damage. The isotope used in these experiments was Ni63, 
13

which emits β particles with 17.4 keV energy. This energy can be absorbed by a >40-μm layer 

of Si without creating any significant defect in the semiconductor. The Ni63 used in these 

experiments were 2-mm circular foils and the SiC diodes used for the preliminary work were 

5 mm × 5 mm SiC square diodes. In order to increase the rate of emission (and therefore the

generated current), we need to increase the activity of the radioactive foils. Ni63 foils are 

commonly used for detection of explosives in Homeland Defense initiatives and as a power 

source for remote instrumentation. 

Alternative isotopes with the long half-lives and low-energy beta emission exist. Half-lives 

greater than 50 years are useful, because then batteries could be designed to last the lifetime of 

the infrastructure. Sensors buried inside buildings that operate the lifetime of the structures 

would require no maintenance. The other useful characteristic of a beta source is that the beta 

(electron) emitted has a low energy reducing potential for radiation damage to the semiconductor 

converter. Ni63 has a 101-year half-life and a 17 keV average beta energy. Three other isotopes 

with similar parameters are (1) Tb157 with a 99-year half-life and 63 keV average beta energy;

(2) Sm151 with a 90-year half-life and 76 keV average beta energy; and (3) Pt193 with a 50-year 

half life and 56 keV average beta energy. 
14

6. References

1. Blanchard, J. P. Stretching the Boundaries of Nuclear Technology. The Bridge 2002, 32 (4), 

29–34.

2. Ahearne, J. F. The Future of Nuclear Energy, editorial. The Bridge 2001, 31 (3), 3.

3. Bugliarello, G. Our Energy Future, editorial. The Bridge, 32 (2), 3–4.

4. Lal, A.; Blanchard, J. The Daintiest Dynamos. IEEE Spectrum Sept. 2004, 36–41.

5. Lal, A.; Blanchard, J. By Harvesting Energy from Radioactive Specks, Nuclear 

Micrbatteries Could Power Tomorrow’s Microelectromechanical Marvels-And May Be Your 

Cellphone Too. IEEE Spectrum, September 2004, 36–41.

6. Litz, M.; et al. On-Demand High Energy Density Materials, Proceedings of 3rd IECEC, San 

Francisco, CA.

7. Guo, H.; Lal, A. Nanopower Betavoltaic Microbatteries. The 12th International Conference 

on Solid State Sensors, Actuators and Microsystems, Boston, 8–12 June 2003.

8. Guo, H.; Yang, H.; Zhang, Y. Betavoltaic Microbatteries Using Porous Silicon, MEMS 

2007, Kobe, Japan, 21–25 January 2007.
15

List of Symbols, Abbreviations, and Acronyms

DEC direct energy conversion

I-V current versus voltage

NSWC Naval Surface Warfare Center

RFID radio frequency identification

SA situational awareness

Si silicon

SiC silicon carbide
16

No. of

Copies Organization

1 ADMNSTR

ELECT DEFNS TECHL INFO CTR

ATTN DTIC OCP

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1 DARPA

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1 OFC OF THE SECY OF DEFNS

CD ATTN ODDRE (R&AT)

THE PENTAGON

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1 US ARMY RSRCH DEV AND ENGRG

CMND

ARMAMENT RSRCH DEV AND ENGRG

CTR

ARMAMENT ENGRG AND TECHNLGY

CTR

ATTN AMSRD AAR AEF T J MATTS

BLDG 305

ABERDEEN PROVING GROUND MD

21005-5001

1 PM TIMS, PROFILER (MMS-P)

AN/TMQ-52

ATTN B GRIFFIES 

BUILDING 563

FT MONMOUTH NJ 07703

2 US ARMY ARDEC

ATTN AMSRD AAR AEM L

 S GILMAN, BLDG 65S

ATTN AMSRD AAR MEE W 

S SINGH BLDG 3022

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No. of

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1 US ARMY INFO SYS ENGRG CMND

ATTN AMSEL IE TD A RIVERA

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1 COMMANDER

US ARMY RDECOM

ATTN AMSRD AMR W C MCCORKLE

5400 FOWLER RD

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DEPOSITORY RECEIVING SECTION

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1 US ARMY RSRCH LAB

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21005-5066

16 HCS US ARMY RSRCH LAB

2 CDS ATTN IMNE ALC HRR MAIL &

RECORDS MGMT

ATTN RDRL CIM L TECHL LIB

ATTN RDRL CIM P TECHL PUB

ATTN RDRL SED E G MERKEL

ATTN RDRL SED E J TATUM

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 (12 COPIES)

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TOTAL: 29 (25 HCS, 1 CD, 3 ELECT)